Advise for which JR pass to purchase

Hi

We will be visit Japan from 28 Mar till 12 Apr 2014 and arrival Osaka Airport on 28 Mar.

We plan to stay in Osaka for 4 Nights,
Day 1 at Osaka
Day 2 at Osaka,
Day 3 visit Kobe
Day 4 visit Nara.
Day 5-8, on 1st April, travel to Kyoto and stay 4 Nights
Day 9, travel to Hakone-Yumoto
Day 10 at Hakone
Day 11, travel to Kamakura
Day 12-15, will be at Tokyo
Day 16 depart at Narita Airport.

Please advise What is the best travel option/pass to use/buy for this trip?
Should i get 14days pass or 2 separate 7 days pass to cover the whole journey?
May i know what are difference between Osaka unlimited 2 days pass and JR pass?

Looking for your reply