Do you have to get an S your self to get a box, or can some one else get one for you?

if they are in a premade they can but you cant with some random you just met

All S ranks : S+, S, and S- count. If you or another player that you QEUEUED WITH gets one of the above ranks, yes, you get a chest.

It counts for the champion you are playing as, so if you got one already you won't get another.

Only if the person who got the S is premade with you, if it's a stranger, it doesn't count.

A viable strategy is to grab a champion you're not good with and have some super carry friend earn an S for you to get an S.

aww lame i got no friends so no boxes for me. thx for the replys.