I want to own a 4 OG letter tag

You could use it now, but you'll be given a suffix. There's also other people with the same tag so even if the original gets freed up, you'd still be given a suffix if you were to take it.

The # and numbers you see at the end of tags sometimes.

all i can say is keep trying your luck and hope for the best alot of 3 letter 4 letter names were taking during the og xbox days and 360 days

sF immediately makes the tag look random to me, just saying.

I'd try and go for something that's original that has no random letters like sF, OG, xX etc.

For 4 letter gamer tags you only have several thousand combinations, you automatically eliminate a lot of words so yes this is very rare, somewhat of a status symbol for some. And the other one may be considered OG since it is a shorter word again hard
to come by now. The other gamers are probably paying you a compliment.