Do you have to be stealthed to get the backstab multiplier?

Do you get any bonuses for attacking from behind if the opponent is busy attacking a follower/minion?

Does it matter if your stealthed or not if they can 'see you' and your behind them while they attack your follower/minion?

You must be sneaking, and the only backstab bonus is from a pair of gloves obtained during either the "destroy the dark brotherhood" quest. or when you join the dark brotherhood.

Or the perk...

I think the perk is for sneak attacks in general, or maybe it is backstabs.