Is the min lending time 1 day?
If I borrow 1000 usd for 2 hours , I need to pay 1 day interest or 2/24 of 1 day interest?
Lending is atomic to 1 hour increments - if you borrow for 0-60 minutes, you pay 1 hour, 61-120 minutes 2 hours etc.
Interest that was generated in the past 24 hours is paid to lenders at midnight, UTC. Borrowers pay the interest when closing their position, until then it is just displayed as fee to them.