is it possable to finish the game without dieing without cheats

If you mean Live, Yes. Play big team battle, and you must be on one of the big maps. If you get a quick early lead many players on the other team might quit and it's relativley easy to not get killed that way. On Coagulation get in one of the tanks. It's hard because of the rockets but I just survived the other night this way without getting killed. On Waterworks, get in a banshee. Fly up to the ledge above where the human sniper rifle lays. You can just stay there the whole game without getting killed. If you can bring one of the sniper rifles up with you you can even get kills. On the smaller maps it's virtually impossible.

I assume you mean on legendary. I play legendary all the time now, firing 4 shots to the head of an elite and then 2 more, "just to be safe" is like second nature to me now. So can you? of course you can, I have probably 3 times, out of the 100+ times I have beat it. I have no free time, so sue me. *anticipation for the next big match with my friends* I am sorry I cannot prove it to you, I don't know how I ever could.

On what difficulty? It really depends how good you are and if your a real strategy person. First off, you need learn the safe area of the stages and where the least enemies are. Than, after you learn all of the safe spots, whenver your low on health or something take cover there. Oh yeah, don't forgert that the weapons matter also. Make sure to have the best weapons on stage. Just try this method for now but I can't guarantee this will work very well unless you are really good at this game... Good luck!