Two questions: 1) In Yu-Gi-Oh, if let's say my opponent uses MSt on my hidden trap card, could I activate it?

Question

Or, if it targets one of my face down MST's could i use it?

I was reading, and that's what the champion did in the 2007 Yu-Gi-Oh tournament?

Also, can anyone link me to a list of their decks?

Like the 2007 champion or the North America champ; Adam Corn?

Answer 1

Yes you could chain a face down trap or MST, unless you set it that turn and on your end phase the opponent activates their face down MST. But once you set that trap and end your turn you could chain to MST or heavy. If you want to see good decks go to tcgplayer.com and deck search decks that have placed in major tournaments.

Answer 2

Yes the trap can be activated as a chain to MST.  

A site to check top deck lists would be metagame.com