Some questions about upcoming Japan trip

I was very excited to ifnd this site! I see from the other answers that you really give excellent o the point answers so thank you!

I am in Khabarovsk Russia and will be flying to Tokyo for a month on Tuesday - or maybe later in the week.

I have a few questions about the rail pass and perhaps you can advise me about my trip in general.

1. I don't see where I can buy a pass here. I am not local and do not speak Russian. Can you tell me where it is possible to purchase a pass here - or alternatively to purchase it online? And obtain the exchange notice to pick it up at Narita airport?

2. there are two scenarios: scenario 1 I am in Japan for a month. Scenario 2 I am in Japan for two to three weeks and that time is separated by a trip to india ( yes I know, a bit crazy... But long story).

I do not have clear itinerary plans as I am there to do research on some ecological practices. I will probably have time left over and would welcome advice you have.

What I do know

I will be in

Tokyo
Mt fuji
Kyoto
Shiga prefecture
Himeji
Miyazaki
Minimata

And probably other places too.

What do you recommend regarding the rail passes? Buy a 21 and 7?

Or possibly go down to Miyazaki during the 21 days and then the end in middle section where there is a cheap overnight bus option back to Tokyo?

Any other recommendation?

1. Can you tell me what the difference is between economy and first class? I am on quite a budget so probably will choose economy but just wondering?

Thanks very much!!