Help with JR pass please!

Hello! My friends and I are visiting Japan (arriving in Tokyo on 28th October) for 2 weeks (departing on 12th November from Tokyo). Our itinerary is as follows - Tokyo>Nagoya>Kyoto>Nagano>Iwate>Tokyo

My questions are:
1. When should I book the JR pass for this trip starting in October?
I was advised since the booking is valid for 90 days, I should book it in mid-august. Is that right?

1. How do I use JR pass (which lines) for this itinerary?

Thank you so much for your help!