1. The rollover
You can only rollover once from traditional IRA/401K/ROTH IRA to HSA. You'll have to be eligible for HSA at least 12 months before the rollover, this means you'll have to be on a HDHP plan for one year.
2. Advantage of HSA
a) no required minimal withdrawal; b) medical expense is paid without paying income-tax.
3. Withdrawing for non-medical reason from HSA
a) you'll have to pay income tax for non-medical withdrawal
b) if you are under 65, you'll have to pay 20% penalty for non-medical withdrawl
c) if you are over 65, you don't pay 20% pelanty.
