Thank you for your words @fdpower
Okay, now i think i have two options to remain in status.
1. Register for classes and maintain f1 status
2. going back to f2
3. Staying in TPS and illegal status

Firstly, i cannot register for reduced course since my TPS status is not approved yet(am i correct?), though i have EAD and Social Security Number through TPS. i don't think it will get approved by the end of January. Secondly, I do not want to register for full courses (huge money) since i'm planning to apply for next Fall. I have been talking to Program director for graduate study and it is almost sure that i will get graduate assistant ship for another program.

I'm thinking about to abandon present F1 status (was planning to study paying tuition fee before TPS things) now and stay in TPS only for 6/7 months. Is it possible to come back in F1 status again after 6/7 months (for different program/new i-20) from TPS status only?

If not, i'm ready to go back to F2. For this, I think i should leave US (correct me if i'm wrong) before my f1 get expired (i have 15 days only for that). What happens to my TPS status if i leave US now and come back in another F2 VISA? (ahh! alot confusion)

Please, suggest me what is the best thing to do in this situation.