I'm 18 and I keep getting messages from people asking if it's legal because I'm only 18 I just dont understand the logic there can someone explain
That sounds odd, because other than alcohol you are of age to do anything. Sounds like they are thinking of more than cuddling.
You are over the age of consent and are able to make your own choices. You are not a child anymore whom brain has not fully developed.
Honestly if they're that stupid I'd ignore or block.
Mostly likely trolls or time-wasters unworthy of your time.