Need advice on how to handle H4 -> F1

Mine is India EB2, PD - May 2015. My daughter, born in November 2006, is currently pursuing her second year of Electrical Engineering at Purdue University. She is maintaining H-4 dependent status.

We have about 14 months before my daughter turns 21 and ages out, and I'm trying to determine the best time to apply for her F-1 status.

Question 1: If the DOF becomes current (for example, in October) and I file her I-485, but the FAD does not become current before she turns 21, can I apply for her F-1 status a few months before she ages out? Would the prior I-485 filing create any issues for the F-1 application because it shows immigrant intent?

Question 2: Would it be better to apply for her F-1 now (using premium processing) and get it approved first? If the DOF becomes current later, can I still file her I-485 as my dependent while she is in F-1 status? In other words, does having F-1 status affect her eligibility for adjustment of status in the future?