Side scroller , fight 2d?

hello guys, i have many doubts about making a game of fight in 2D, like SF, MK, injustice where the game is fully 3D with 2D view, all files and characters are 3D, my doubt is: to make a enemy suffer damage is the same thing of the various tutorials on melee combat ?, I made a estensa search but got no answer many of the doubts I have,
my doubts that besides the already mentioned above are

the animations are different from the template of the third person?

how do I create combos?

how do I support two players 1vs1 (choose character / choose map to the fight)?

a doubt my now comes on modeling, modeling after the character in zbrush and decrease the 10k polygonos what is the next step to import it to the unreal? I mean, I have to do his skeleton in Maya, but how?

how is the effect where the camera approaches the character in particular, or flashes, or something showing that a super special has been activated?

sorry my english , i’m using google translate.