-Is it fine to keep two snakes of different species in the same tank?
NO. Please see this thread:
http://www.cornsnakes.com/forums/showthread.php?t=31192&page=1&pp=10
and this thread:
http://www.cornsnakes.com/forums/showthread.php?p=261720#post261720
-How many hides should I keep in the tank?
Most would recommend one per temperature gradient, so if you have a warm side and a cool side go for 2 hides if not more.
-Feed them in seperate containers?
Seperate to each other? Absolutely.
Feed in the same container and any of the following can happen: One snake eats all the food and becomes dominant so one withers away. One snake decides that the other smells pretty mouse-like and eats it. One defends the food from the other by biting and disfiguring/kills the other.
Seperate to their vivs?:
Well that depends on a few factors. If your bedding is something they can swallow, then feed in a seperate container. If they accidentally swallow their bedding it can cause blockages inside and they die. You also want to train their striking response so they don't bite you, and feeding them in a specific container can help with this.
-Can I keep more than 2 snakes in 1 tank?
See above, especially corns, NO.
-Does their gender make a difference?
If they are going to eat each other, not so much. They'll eat their cell-mate either way. Also the whole passing-on-diseases, mating-and death-through-too-early-eggs, one-escapes-so-the-other-escapes stuff to factor in. Mainly, NO, and then again............... NO. If a girl will eat a girl for whatever reason, she'll eat a boy too.
-Is it possible that they might mate if they were of the same species and ofcourse different gender (im still a beginner, i dont want to end up with alot of babys)?
Yes it is possible, no you wouldn't like the outcome. E.g Eggs you aren't equipped to deal with, egg-bound females, stressed snakes who won't eat anything, parasite exchanges.............
Your questions were very well thought out and I applaud you for asking them. I hope you don't take my aggressive-advice in the wrong way. Just be aware that this question is often raised, and as there will be a few who tell you to co-hab, just use the search function to find out how many will warn you against it. I don't want to see more pics of cannibalised snakes!
All the very best with yours, I hope you enjoy them as much as I enjoy mine!