1. Can I reenter US based on valid I-94?
>>You need a valid H1 visa to enter the US. You will surrender the I-94 before you leave. You will get a new I-94 when you enter.
2. Will it impact my GC process?
>>Not if you enter on an H1-B visa. However, since your AP is not yet approved, if you use AP you are abandoning your GC process