*Sigh* Go with Unity. Games are about a lot more than shiny, 3k textures. Once you draw all that real-time glory, that AI still has to go somewhere. Monogame is a framework, a wrapper of sorts, built around XNA, which was an API. Unity is like a cookbook. Monogame is The equivalent in kind to to giving you a blank book,and saying "here kid, write your own recipes. There's also www.gameinstitute.com as well. It costs about 99 dollars, but you learn a lot. www.3DBuzz.com also has some tutorials. Moral of the story: Go with Unity. I noticed you never even mentioned a little something like an image manipulation program. If your school permits, I would go with photoshop. If not: www.gimp.org. There's also an online photo editor named pixler.

The answers to your questions are as follows:

Direct3D and OpenGL -- put them in a file and just walk away, right now. DirectX is a complete set, comprised of numerous API's. Direct3D is mainly resposible for drawing anything you see on the screen.

OpenGL is Direct3D's main competitor -- it's also portable. If you write a game in DirectX, you're mainly targeting windows. Opengl works on Linux and Mac. SDL, can use both OpenGL and DirectX

There's also Allegro and Love2D. No, 2D game programming isn't difficult, but networking adds another nitch to the game. All you need to get started is essentially Microsoft paint, and an IDE, the arduous part is coding the beast. Any other advice? Go with Unity!

I am not sure if I should agree here or not. My gut says to use pre written libraries where possible if you are on a tight deadline, but the learning curve for these libraries has been glossed over. In terms of complexity comparing learning unity and xna/monogame is like comparing learning to drive a car and fly a helicopter. Xna/monogame is simpler and includes all the basics needed - 2d sprite manipulation, sound, input and platform independence.

Given this, why spend 6 of those seven months learning all of unitys toolkit when the game could be finished in a month by any competent c# programmer with a little time in monogame. Oh, and monogame is free, so no need to buy a license for software which is essentially a school project...

Back when I started on my current game project I evaluated XNA but was disappointed because I wanted more control over what was going on. I ended up going with SlimDX, which is a wrapper around DirectX which can be used in .net. It doesn't hold your hand at all, it's exactly like the blank recipe book analogy cited by Code_Grammar, but that's exactly how I like to roll.

That said, it was fairly daunting to get a working game engine up and running. But now that I've put in the effort I'm really proud of what I've achieved. If I ever get more heavily involved with games development it should provide a good base skill set.

I'm not saying its the right way to go for you, something like Unity or Monogame might be more appropriate, but thought I'd add it to your potential options.