Here's my completion. The quality isn't as good nor is it a speed run/wr attempt but it was fairly challenging.

I definately have all the silver objectives done save a couple. I'm sure I've got a few Gold ones done. I don't think I have the time to do all the 'gold' challenges.

I'm sure I can do all the Gold challenges since there's no level cap. Celes and Terra NMG would be easy if there's no level limit.

YouTube - Kefka Final Battle Low Level Completion (B Category)