What hardware information can I get from a guest OS

Hi, My application is using hardware information such as CPU name or chipset information. I have 3 questions.

1. Are these different from the ones I can get when I install an OS without virtualization?

2. Are there any way to change this info, either by settings of Xen or by using APIs?

3. Can applications recognize whether they are running on a virtual machine or not?

Thanks