Like billions before me I decided to make a WW2 game. It's about a german soldier who rebels against the german army. I've already got the story figured out but I need help with the levels. Up til now I've made 3 levels. I welcome any suggestions or ideas for the game.

However I have some questions that I would like to ask since it impedes me of taking my project further.
QUESTIONS:
1-I have problems whith the edges of my levels. I don't want the character to fall off the edge of the level but I don't want to just put a wall to block the view either. Can I put an invisible barrier of some sort? Any other strategies that I can use to make outdoor levels look more vast?
2-I saw interesting material
here. The are 2D plants and trees, there is tall grass, the sky and horizon are different and also the road and the grass have a texture that "blends" them together. How can I do all that? Does it necessary involve using 3d world studio?
3- What's the difference beetween shoot.fpi and shoot10.fpi
4- Any ww2 packs you would recommend besides the standard one?
Thanks for your patience and I hope you can enlighten me with your knowledge!