Question on H4 to H1B

I am in H4 status and a company is applying for a new H1 for me now. In the initial I-129 H1B application, the employer chose the option to let me get a visa at an oversea US consulate and the petition got approved. In this case, do I still have any option to change status from H4 to H1 without leaving the U.S.?

In addition, if I don't go abroad to obtain an H1B visa, will the new H1B become valid upon its approved starting date, and will my H4 status expire at the same time?

Thanks a lot.