Can i work for old Employer on Old H1B Petition that is still valid?

[Psha]

Summary

• I worked for Employer A till Feb 2022 on H1B. 
• Joined Employer B in Feb 2022 after H1B Transfer and worked for them till November 2022.
• Joined Employer C in November 2022 and Currently working for them.
• Now my Employer A wants to hire me back in the exact role/same location as before.

Questions

1) Employer A never revoked my H1B petition, and it's still valid till January 2024. Do they have to file a new LCA/H1B petition, or can I work for them on the existing H1B that is still valid? (As per the attached Screenshot)

 

2) If I can work for Employer A on the existing H1B petition, How does USCIS know that I am employed by Employer A but not by Employer C.?

 

3) Also, I have a Dropbox Visa stamping appointment scheduled for April End 2023. If i join Employer A on existing (Valid) H1b, will this cause any issues with my visa stamping?

[JoeF]

The old employer was required by law to inform USCIS that you no longer work there. If they didn't they would have to pay you for all the time since you left. No sane employer would want to do that, so you can be sure that their HR has informed USCIS. If they want to hire you back they have to file a new LCA and H1 petition.

[pontevecchio]

There was a similar post which may be of interest.

Can I go back to my old employer? - H1B : General - Murthy Law Firm