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Regular expression to match capture group not preceded by certain characters

I want to write a regex that will match if and only if the pattern is not preceded by the characters "Etc/".
Strings that should match:
GMT+01:00
UTC+01:00
UTC+01
+01:00
...
Strings that should not match:
Etc/GMT+01:00
Etc/UTC+01:00
Etc/UTC+01
...
This is what I have so far:
(?<!Etc\/)((UTC|GMT)?(\+|\-){1}(\d{1,2})(:|\.)?(\d{1,2})?)
The right part of the above regular expression already matches the UTC and GMT offset and covers all the cases I need. But I don't manage to implement the exceptions mentioned above.
I expected the above regex to not match the string Etc/GMT+1:00. But in fact it matches the part +01:00 and only ignores Etc/GMT.
How can I achieve that the the following regular expression does not match if it is preceded with "Etc/"?
(UTC|GMT)?(\+|\-){1}(\d{1,2})(:|\.)?(\d{1,2})?
Here I have an example with most of the use cases I need.

You may add \S* after Etc/ to make sure Etc/ is checked even if there are any zero or more non-whitespace chars between Etc/ and the expected match:
(?<!\bEtc/\S*)((UTC|GMT)?([+-])(\d{1,2})[:.]?(\d{1,2})?)
See the .NET regex demo
Details:
(?<!\bEtc/\S*) - a negative lookbehind that matches a location that is not immediately preceded with a whole word Etc/ and then zero or more non-whitespace chars
(UTC|GMT)? - an optional substring, UTC or GMT
([+-]) - + or -
(\d{1,2}) - one or two digits
[:.]? - an optional : or .
(\d{1,2})? - an optional sequence of one or two digits (equal to (\d{0,2})).

As you are already capturing all data in groups, another way could be getting all the matches of Etc/ out of the way, and use your pattern to capture what you want in the groups.
Note that you can change groupings of single chars like (:|\.) to a character class ([:.])
\bEtc/\S*|(UTC|GMT)?([+-])(\d{1,2})([:.])?(\d{1,2})?
\bEtc/\S* Match Etc/ and optional non whitespace chars
| Or
(UTC|GMT)?([+-])(\d{1,2})([:.])?(\d{1,2})? Your pattern with all the separate groups.
Regex demo
Or with just a single group:
\bEtc/\S*|((?:GMT|UTC)?\+\d{2}(?:[:.]\d{2})?)
Regex demo

Find regex pattern match string have multiple condition?

I have some strings formatted as follows:
1=case1,case2,..caseN;2=case1,..,caseN;3=case1, ..,caseN
Note: comma ";" is used to separate cases and case1, case2 are anything like strings, number doesn't matter their type.
I want to find regex pattern to match string
1=home,house;2=abc;3=2019,2021
however, it will not match the following:
1=home,;2=abc;3=2019,2021 (Excess comma mark at case 1)
1=;2=abc,2012;3= (must 1=..; not 1=;)
1=home,age;2 (must 2=.. not 2)
2=home;;3=sea (must ;3 not ;;3)
4=flower;k3=sea (must 3= , not k3)
I tried with the pattern: (\d+={1}[^;]+;). However, it will match if the backstring is not.
Please show me the way.
Many thanks!

Maybe this pattern helps you out:
^\b(?:(?:^|;)\d+=[^,;]+(?:,[^,;]+)*)+$
See the Online Demo
^ - Start string ancor.
\b - Word-boundary.
(?: - Opening 1st non-capture group.
(?:- Opening 2nd non-capture group.
^|; - Alternation between start string ancor or semi-colon.
) - Closing 2nd non-capture group.
\d+= - One or more digits followed by a =.
[^,;]+ - Negated character class, any character other than comma or semicolon one or more times.
(?: - Opening 3rd non-capture group.
, - A comma.
[^,;]+ - Negated character class, any character other than comma or semicolon one or more times.
)* - Close 3rd non-capture group and make it match zero or more times.
)+ - Close 1st non-capture group and make sure it's matches one or more times.
$ - End string ancor.
Note: I went with a negated character class since you mentioned "case1, case2 are anything like strings, number doesn't matter their type", therefor I read there can be spaces, special characters or any kind other than comma and semicolon.

This works on regex101
^(?:\d=(?:\w{1,},)*(?:\w{1,});)*(?:\d=(?:\w{1,},)*\w{1,})$

^(?:\d+=[a-z\d]+(?:,[a-z\d]+)*(?:;|$))+$
Demo
^ : match beginning of string
(?: : begin nc group
\d+=[a-z\d]+ : match 1+ digits, then '=' then 1+ lc letters or digits
(?:,[a-z\d]+) : match ',' then 1+ lc letters or digits in nc group
* : execute nc group 0+ times
(?:;|$) : match ';' or end of string
)+ : end nc group and execute 1+ times
$ : match end of string

I don't know if c# supports recursive pattern, but, if it does, use:
^(\d+=\w+(?:,\w+)*)(?:;(?1))*$
if it doesn't:
^\d+=\w+(?:,\w+)*(?:;\d+=\w+(?:,\w+)*)*$
Demo & explanation

How to match a string between <>?

I tried \w+\:(\w+\-?\.?(\d+)?) but that is not correct
I have following text
<staticText:HelloWorld>_<xmlNode:Node.03>_<date:yyy-MM-dd>_<time:HH-mm-ss-fff>
The end result I want is something like the following
["staticText:HelloWorld", "xmlNode:Node.03","date:yyy-MM-dd","time:HH-mm-ss-fff"]

You could use the following regex.
<(.*?)>
Then have a look at how groups work to retrieve the result.
Regex rx = new Regex("<(.*?)>");
string text = "<staticText:HelloWorld>_<xmlNode:Node.03>_<date:yyy-MM-dd>_<time:HH-mm-ss-fff>";
MatchCollection matches = rx.Matches(text);
Console.WriteLine(matches.Count);
foreach(Match match in matches){
var groups = match.Groups;
Console.WriteLine(groups[1]);
}

This line should be able to match the content:
<(.*?)>
It will catch the arrows at the end which you don't seem to want, but you could remove them after words without regex.
You should consider a website like https://regexr.com - it helps exponentially in writing regex by allowing you to paste your cases and see how it works with them.

Matches any string within the <>. Hope this helps.
<(.*?)>

Your pattern does not match the 3rd and the 4th part of the example data because in this part \w+\-?\.?(\d+)? the dash and the digits match only once and are not repeated.
For your example data, you might use a character class [\w.-]+to match the part after the colon to make the match a bit more broad:
<(\w+\:[\w.-]+)>
Regex demo | C# demo
Or to make it more specific, specify a pattern for either the Node.03 part and for the year month date hour etc parts using a repeated pattern.
<(\w+\:\w+(?:\.\d+|\d+(?:-\d+)+)?)>
Explanation
< Match <
( Capturing group
\w+\:\w+ Match 1+ word chars, : and 1+ word chars
(?: Non capturing group
\.\d+ Match . and 1+ digits
| Or
\d+(?:-\d+)+ Match 1+ digits and repeat 1+ times matching - and 1+ digits
)? Close non capturing group and make it optional
) Close capturing group
>
Regex demo | C# Demo

C# equivalent for this regex pattern

I have this regular expression pattern: .{2}\#.{2}\K|\..*(*SKIP)(?!)|.(?=.*\.)
It works perfectly to convert to replace the matches to get
trabc#abtrec.com.lo => ***bc#ab*****.com.lo
demomail#demodomain.com => ******il#de*********.com
But when I try to use it on C# the \K and the (*SKIP) and (*F) are not allowed.
what will be the c# version of this pattern? or do you know a simpler way to mask the email without the unsupported pattern entries?
Demo
UPDATE:
(*SKIP): this verb causes the match to fail at the current starting position in the subject if the rest of the pattern does not match
(*F): Forces a matching failure at the given position in the pattern (the same as (?!)

Try this regex:
\w(?=.{2,}#)|(?<=#[^\.]{2,})\w
Click for Demo
Explanation:
\w - matches a word character
(?=.{2,}#) - positive lookahead to find the position immediately followed by 2+ occurrences of any character followed by #
| - OR
(?<=#[^\.]{2,}) - positive lookbehind to find the position immediately preceded by # followed by 2+ occurrences of any character that is not a .
\w - matches a word character.
Replace each match with a *

You can achieve the same result with a regex that matches items in one block, and applying a custom match evaluator:
var res = Regex.Replace(
s
, #"^.*(?=.{2}\#.{2})|(?<=.{2}\#.{2}).*(?=.com.*$)"
, match => new string('*', match.ToString().Length)
);
The regex has two parts:
The one on the left ^.*(?=.{2}\#.{2}) matches the user name portion except the last two characters
The one on the right (?<=.{2}\#.{2}).*(?=.com.*$) matches the suffix of the domain up to the ".com..." ending.
Demo.

How to insert spaces between characters using Regex?

Trying to learn a little more about using Regex (Regular expressions). Using Microsoft's version of Regex in C# (VS 2010), how could I take a simple string like:
"Hello"
and change it to
"H e l l o"
This could be a string of any letter or symbol, capitals, lowercase, etc., and there are no other letters or symbols following or leading this word. (The string consists of only the one word).
(I have read the other posts, but I can't seem to grasp Regex. Please be kind :) ).
Thanks for any help with this. (an explanation would be most useful).

You could do this through regex only, no need for inbuilt c# functions.
Use the below regexes and then replace the matched boundaries with space.
(?<=.)(?!$)
DEMO
string result = Regex.Replace(yourString, #"(?<=.)(?!$)", " ");
Explanation:
(?<=.) Positive lookbehind asserts that the match must be preceded by a character.
(?!$) Negative lookahead which asserts that the match won't be followed by an end of the line anchor. So the boundaries next to all the characters would be matched but not the one which was next to the last character.
OR
You could also use word boundaries.
(?<!^)(\B|b)(?!$)
DEMO
string result = Regex.Replace(yourString, #"(?<!^)(\B|b)(?!$)", " ");
Explanation:
(?<!^) Negative lookbehind which asserts that the match won't be at the start.
(\B|\b) Matches the boundary which exists between two word characters and two non-word characters (\B) or match the boundary which exists between a word character and a non-word character (\b).
(?!$) Negative lookahead asserts that the match won't be followed by an end of the line anchor.

Regex.Replace("Hello", "(.)", "$1 ").TrimEnd();
Explanation
The dot character class matches every character of your string "Hello".
The paranthesis around the dot character are required so that we could refer to the captured character through the $n notation.
Each captured character is replaced by the replacement string. Our replacement string is "$1 " (notice the space at the end). Here $1 represents the first captured group in the input, therefore our replacement string will replace each character by that character plus one space.
This technique will add one space after the final character "o" as well, so we call TrimEnd() to remove that.
A demo can be seen here.
For the enthusiast, the same effect can be achieve through LINQ using this one-liner:
String.Join(" ", YourString.AsEnumerable())
or if you don't want to use the extension method:
String.Join(" ", YourString.ToCharArray())

It's very simple. To match any character use . dot and then replace with that character along with one extra space
Here parenthesis (...) are used for grouping that can be accessed by $index
Find what : "(.)"
Replace with "$1 "
DEMO