I'm new to 3D modeling, but have learned a whole lot in a few days. I am putting the finishing touches on my first model, a car which will hopefully be used for a video game, ultimately. I have 4 newbie questions:

1) I am trying to reduce polygon counts as much as I can, so there are a few instances where I have a large true rectangle shape (see attached picture), but then below it I needed to add more geometry for other elements of the car, however this creates extra vertices on my large rectangle, as well. The question is, is it now necessary to cut lines through the true rectangle (with extra vertices) in order to make it not be an N-Gon?

2) What happens if I have a series of mirrored extruded edges (mirrored down the middle, to create my car) that connects at many places, but DOESN'T connect along the bottom side body kit? (see picture) This part is currently represented as a 2D plane.. will it still render? Or is this bad practice? If it became "invisible" from certain angles (being 2D), and I decided to extrude a small lip that goes back underneath the car, what if wasn't able to connect the final 2D plane that you can't see underneath the car? Will this cause errors when rendering, or is the punishment simply that the 2D plane will become invisible from certain angles?

3) Is it considered the norm to subdivide once or twice when putting a car model in a video game? My car is an old Toyota Corolla lookalike (very square, sharp edged car) and when I subdivide, it gets way too rounded. I am perfectly OK with it being exactly how it is at zero subdivision, but if I decide to subdivide other cars to be used in the same game, is it necessary to do it with this car as well? Also, is there any way to choose to only subdivide certain parts to keep straight lines where you want them? (I use Silo)

4) I am very confused on what is and is not allowed for surface normals.. is it true that any two planes that share a line cannot form an acute angle? If so, it would seem impossible to do almost anything... Anybody mind explaining this for me or pasting a link?

Thank you all in advance very much for helping me out!!

vertices.JPG 14.51 KB Views: 919 Description: Large Rectangle Quad with Detail Section UNDERNEATH It

2Dplane.JPG 9.46 KB Views: 919 Description: 2D Plane