Can you get an F visa for more than 3 months?

Hi

I posted this the other day but cannot find it so apologies if you have already answered it.

My partner is going to Kunming to study kung fu. He has an invitation from the school. He would like to stay for 3 months then spend maybe 2 weeks travelling around China. Is it possible to get an F type for longer than 3 months? Also, is it actually 3 months or 90 days that they are normally valid?

Many thanks