Can a few-year-old company with one employee hire a C2C employee and sponsor his/er H1b? Yes

You will need a petitioning employer and usually employer hires an attorney to file their PERM, I-140.

Best to seek entry on H-4 instead of filing COS

F-1 is difficult for certain country nationals, whereas H-4 is much easier. Completion of F-1, OPT is available. H-4 EAD can be procured based on...

COS can be filed by prospective employer. If subject to cap, the window opens in April.

B-2 is always difficult with pending I-130

Similar question asked earlier. Please see earlier response regarding requirements.

I-94 is to be valid when extension is pending.

Passport not expiring for 6 months can be used to apply for COS

It depends on the bases for applying AOS.