H4 to H1- change of status

[victory]

Hello Frnds,

I hold a valid H4 and travelled to the US several times. I filed for a H1 this May as a fresh applicant from India. I am still waiting for my approval.
Can anyone let me know if I travel on H4 to the US now, can I apply for change of status (H4 to H1) after I get approval and will I be able to work?
And also can anyone tell me the approximate time for change of status.

Regards,
Victory...