1. Can I apply green card while working oversea (in the third country, not the country I hold citizenship for) for an US company?
-Yes.
If the US company issues payroll in US, what my status will be?
-Not applicable. You do not have any non-immigration or immigration status related to U.S. at present. You need to pay tax to China and/canada (should have some kind of agreements), not to U.S.
Will H1-B/TN work in this case? What restrictions there are?
--Not applicable.
2. Can company do PERM and I-140 while I work oversea?
-Yes.
3. Can I apply CP in lieu of I-485?
-Yes, that is the only way when you are not physically in U.S.
What if my H1-B reaches 6 years cap and my PD is still not current?Am I able to extend my H1-B at that time?
-You do not have H1 status and you have to wait for the PD become current for the PC interview.
If I don’t have a working status in US, will CP still work for green card application because I am outside of US?
-Yes, the PC is just for the situation like you.
THANK YOU ALL!!