7th year extension with multiple employers - bridging

[SHR12]

My situation:

1. While on H1B with Company 'A' filed for PERM and I140 thru company 'B' and got both approved
   
2. Filed for 7th year extension with Company 'C' before I94 expired with Company 'A' and started working for company C
   
3. while 7th year extension with company C is pending with USCIS, filed for another H1B extension with company 'D' and started working for D. RFE received and replied. H1B got denied.
   
4. Been on projects continuously and paid salary.
   

Questions:

1. Since first H1b extension filing is still pending with USCIS with company C, can I stay in US and work for company C
   
2. If I appeal against the denial of H1 filing of compnay D, can I work for Company D
   
3. Since I140 is approved, and H1b extension is pending thru company C, Can I file for H1B thru another company.
   
4. What are my options to stay legally and work in US, till I get EAD.
   

Appreciate your time and help in advance.