Re: Adjusting aspect-ratio
There is no matrix stack on an OpenGL ES 2.0 implementation, just as with OpenGL 3.x and newer, the fixed function pipeline has been removed and a lot of the initial functionality in OpenGL 2.0 shaders have also been removed.
Thus, gluPerspective is not being used anymore, nor any matrix operations at all.
What you're probably looking for is using uniforms. You need to define your own uniform matrices in your shaders and supply them with your own calculated values. Google for gluPerspective and you'll find the code used for the matrices in the specification.
If you're looking for an implementation that do support all of this, and you do not plan to use shaders, i would recommend looking at OpenGL ES 1.x instead.