Support Amumu?

Not really. I tried it a couple of times. Basically leona support but less tanky and higher cooldowns.

Not really. Amumu doesnt offer anything as protection. Also on early levels all he has is his Q, which is crappy version of Leonas E. Any minion can block it. Also he is very mana reliant for his abilities, he cant protect himself. He has strong ulti, but it has high cd.

Nope. The reason being that his Q cannot bypass minions and it pulls him in instead of pulling the target back. This doesn't really work well. True, he has a ult for CC too but keep in mind that it has a very large CD leaving Amumu with 1 form of CC that forces him to all in and that CC has a pretty big CD.