Do I need the JRPass?

Hello,

I'll be visiting Japan in October, arriving in Tokyo Haneda and connecting to Osaka, Kyoto, Sapporo, Yokohama and adding on Nara and possibly a few more other cities. I plan on staying for about 12 days in total. Do you recommend me buying a JRPass or buying individual train tickets for each city? I should also mention my departure is from Tokyo, so at the end of my itinerary I will have to come back to Tokyo Haneda again for my departure.

On a different note, can I use JRPass to ride on all modes of public transportation to go to places within the same city as well?
Thanks a lot

Gülşen