H4 to convert to F1 or student visa

You can do it before your final semester in many cases, but not later than that. Be aware that your tuition is going to go up significantly since you will now be required to pay the international student rates for everything.

You may qualify for the OPT for maximum of one year but then it does not change anything after that. And in order to maintain the student status, you are going to have to continue on with your studies to be able to remain in the US.