Install and Use Cuda 4.0 together with 3.2?

Hi, have a question…

I have windows 7 and still messing with some nVidia and Sony hybrid GPU drivers for my Vaio Z. I was able to upgrade my
video driver to version 263. Unfortunately it doesn’t allow me to run CUDA 4 examples.

Is it possible to install and use CUDA 4 and 3.2 together considering that I already installed 4 RC2? If yes how can I do it. I don’t want
to touch my video driver. Can CUDA 3.2 use 270 video driver or it’s not backward compatible?

Is it possible to compile code using CUDA 4 or CUDA 3.2 without GPU/GPU video driver with VS 2010 /VS 2008? I’m asking this because
I have access to a Linux
box with GPU fully configured for CUDA 4, but may not have internet all the time and need to play with it.

Is there any GPU emulation mode in CUDA 4.0

Funny, openCL examples from CUDA 4 install work for me with 263 Driver CUDA C examples don’t.
How OpenCL is different from CUDA C in this sense???