Well I am not sure how it works, is it: it can only be used when all of the PP of the other moves are used up or do you only use one of each move then you can use last resort or is it something else?
It like you said on the 2nd Part you have to use at least 1 move Each then you can use "LAST RESORT" then there you go you can use it again without waisting another move.
Yeah, my Jolteon could learn last resort so I know how it works. Once your opponents pokemon uses at least one of each of its moves you can you last resort. Also it dose have a description on the game.