is my old I797 still valid until I get new one approved?

[Dharmateja]

Hi,

I have a valid I797 and stamped visa with company A which will expire Dec, 2019. In between, My current employer where I am working is willing to file a cap exemption using company A's I797 copy. Now my question is,

1. What if current employer receives RFE from USCIS and they don't provide evicence. are my company A's I797 and visa still valid? Can I travel with them?

2. When will my company A's I797 and visa become invalid?

Thanks,