Number of HLSL and Pix Requests

Question

I have a number of studies with HLSL and Pix.

1) Can you declare a pixel shader in HLSL 3 yourself without a vertex shader? If not, what can I do to get around this?

2) Why does the code skip Pix? I have a rather long shader method, but Pix seems to stop me from debugging halfway, and then skips the rest of the block. I set Pix to collect information when F12 hit, and check the DISABLE D3DX analysis checkbox. I have to do this because I use XNA.

3) Can I debug a shader when an experiment is running?

Greetings