H1B amendment two petitions

I had filled h1B mobile amendment in Jan 2018 for A location. Now my project got changed and new amendment going to fill by Jan 2019 for B location. Earlier mobile amendment result is yet to come. So is it valid if two petition can be with USCIS.

If in worst scenario first amendment got rejected, however I already have a new project amendment recipt number then earlier rejected case can impact on my stay in US?

withdraw first amendment and file new amendment. OR amend the pending amendment.