I tagged a char to make it 49 by myself and never go past lvl 50 but now I can't untag it because I need to get XP but if I get XP I need to do the "Get to level 50 quest" which I don't want to do since that char will be a farm all. My suggestion is let us untag chars even if they have more XP because in no way am I making that char 50 just to untag it ....

I ran into this problem the 1st day this new tagging system came out.  You can submit a ticket and they will untag you.  I also posted this same feedback.

I did just that. I now successfully untagged the char. Thank god they have the untag support.