Huairou to Jiankou transit time

Hello,
I'm planning to go to Jiankou from Beijing and return to Beijing on the same day. How long does it take to get from Huairou to Jiankou? And how often does that bus go (every 10 minutes, every 20 minutes etc)?

Finally, is it possible to hike from Jiankou to Mutianyu within one afternoon, like say 2-3 hours?
Thank you.