you box? that's so cool... anyways, i started ballet about six months ago (i was 15, still am now) and i start pre-pointe next month so i'd say it's definitely not too late. you just have to practice a lot at home. practice your routines and combos as well as what you do at the barre and across the floor. the more you practice, the faster you'll catch up to your age level. also, when you practice at home, it shows in class so that'll really show your teacher you're dedicated. you also have to be willing to challenge yourself. i take classes with girls who have been dancing their whole lives and it was really hard at first but i'm catching up. this showed my teacher that i was serious about dancing and contributed to me starting pre-pointe so early. so yeah, if you work hard, it's definitely not too late.
as far as ice skating goes, i honestly have no idea as i've never ice skated before but you're never too old to try something you really want to do so i'd say go for it.
best of luck :)
dancer (hip hop, bboying, ballet, jazz, tap)