1. 3/5
2.
-Nair>utilt
-Nair>bair
-Nair>fair
-Nair>usmash
-nair>nair
-nair>uair
-nair>grab
3. This is probably diddy's best combo move besides bananas and dash attacks. It can combo into so many things especially at low percents. The bad part about this move, though, is that it's hitboxs are fairly small along with being a fairly laggy move. I like to use this move if I have to hit at a diagnol that I know my bair won't hit or something. It's pretty good to use as you're falling down especially if you FF right as you use it to make it more unexpected. If I can get a good nair in at low percents and I know I will go unpunished then I will use it because of it's insane combo ability.
4. As I said before, it's a good move for comboing and to get back on the ground when your opponent is at your back diangol. It's also very good in the olimar MU because it keeps pikmen off of you. You can hold a banana in your hand and z drop it and recatch it with a nair so that way you don't have to put your banana down every time you want to get pikmin off of you.