B2 change to H4, apply inside or outside?

[dodoph]

Im B2 holder and in US right now. My fiance is in H1B with approved I-140. We will get marry in the end of Sep in US. After marriage, I will apply for H4. Can I apply for it inside US? Can I be considered as immigrant intent? If I submit my h4 application haven't receipt it, can I still stay in US with expired B2 status but in process H4 status?

Thank you!