Working in Comp. A and applied H1B Visa through Employer B,VISA Stamping ?

I am an SAP Technical Consultant and working for Company A with an experience of total 5 and half years and Applied for H1B Peition in 2013 through an Employer B (which is in USA) and got approval recently. Currently am working for Company A and will be going for H1B VISA STAMPING later this month end.Please answer my below questions.

1.What is your Current Employer ? ( Do i need to mention A or B )

2.How did you got this opportunity to work with Employer B ?

3.You will be working for Client or Employer?

4.How long you are planning to stay in USA?