Can I renege on the offer of second company during h1b transfer. want to join company c

Hello everyone,

I am working for CompanyA for 2+ years on H1-B. I accepted a job offer with CompanyB and they are processing H1-B for me. I have received a job offer from CompanyC and would like to join them after they process H1B.

When CompanyC applies for H1B petition for me, they will ask for all previous I-797s. When I submit the documents to CompanyC, should I also give them the I-797 from CompanyB? If I have not joined CompanyB, I might not have access to their I-797.

OR is it better to join CompanyB and then quit after 1 month or so to join CompanyC? Will USCIS be cautious if they receive another petition from CompanyC 1 month after receiving a petition from CompanyB.

CompanyB also want to process H4-extension for all my dependents. If I don’t join CompanyB and instead join CompanyC, will there be some issues?

Thanks for your advice.