Work permit and its Rules & Regulatalions

Hi all,

I am very new to this immigration site. I have few queries regarding immigrating to UK on a WP.

#1. One company is sponsoring my WP in Jan 2007. (In Feb i will be there in UK). I have 4 Years of Experience in Siebel + Datawarehousing. Will i able to work with some other company with this WP which is sponsored by Company A.

#2. What are the things that i need to take care when applying for a WP.
do's & dont's or tell my sponsor not to do on my WP

#3. Suppose i work on my WP for 2 yrs, after that i will apply for HSMP,
My tenure for PR is considered whole i,e stay with WP+stay with HSMP.

Please clarify

Regards,
Sekhar