Japan Rail Pass or REgional Pass

HI

I am writing to seek your kind advice on the following.

I am confused over the JR Pass and REgional Pass. I have the following plan to go to Japan on first July and please see my itinerary for your kind reference.

Tokyo (2 nights)
Tokyo to Kyoto (4 nights)
Kyoto to Osaka ( 4 nights)
Osaka to Tokyo (3 nights)

I would like to find out which is more economical for my trip.

1.Should I take a JR Shinkasen from Tokyo to Kyoto?
2. Kyoto -Osaka to take the REgional Pass -Sanyo . But I wish to go to the shirakawago, so which regional pass shoudl I take? I am thinking of taking the regional pass for 7 days
3) Is the JR Shinkasen fee covers 2 ways or just one way? If I take from tokyo to kyoto, (if it covers 2 ways) do I have to pay extra for Osaka to Tokyo as I will be going from Osaka back to Tokyo.

I thank you for your kind attention and look forwrd to hearing from you.