1) You can block simple melee before you get attacked by pressing the "q" key (defult)
In advanced melee its the same thing but you cant avoid the damage only you avoid to be thrown.
Now, if you mean that you get melee'd and then the attacker swoops at you or tele's at you and does a second melee on you, then you cant. Just be carefull so you wont be meleed in the first place
2) No, only one (1) rtansformation is avaliable for each character. There will be more transformations in 1.3v ESF, which will be released when its done (and thats quite a while)