I have come to US on H4 visa and applied for COS to H1B last year. It got approved for 2 years till 2017. My H4 stamp and i-94 is valid till this year end (2016).
My employer didn't show me any project for 7 months & later placed me in a project and started generating paystubs. Now I am planning to apply for COS to H4 EAD.
Since I didn't maintain my H1B visa for first 7 months my COS can be rejected. My questions are:

1. If I resign my job go back to my home country & can I come back to USA with my valid H4 stamping on my passport? Will there be any issue at port of entry?
I am not planning for my Visa stamping in my home country. Will my old H4 stamping be still valid?

2. Is it mandatory to go to home country or any other country works in this case?