Using the Japan Rail Pass multiple times and clarification needed

Hi,

I have some questions about using the Japan Rail Pass, and I’d appreciate your help:

1/ My family will be in Japan for 10 days, but we only want to purchase 7-day Rail Passes. Can we activate our passes on day 3 or day 4 to cover our remaining stay? If that’s possible, where do we activate them? Do we activate them on day 3 (or 4), or can we set an auto-activation for that day when we exchange our vouchers? Can we exchange the vouchers upon arrival on day 1 at Narita Airport and note that we want the passes activated on day 3 (or 4)? We’re also unsure where to exchange the vouchers/cards and what would be the easiest way to get the passes.

2/ Here’s my travel itinerary for the week:

26 March: From Tokyo to Kyoto
29 March: From Kyoto to Osaka
30 March: From Osaka to Tokyo
30 March (on the same day): From Tokyo back to Osaka

I understand the Japan Rail Pass covers Shinkansen lines between these cities. Will our Pass cover all these trips, or will we need to pay extra? Is there a limit on the number of Shinkansen rides we can take back and forth between these cities?

3/ Once our Japan Rail Pass is activated (on day 3 or 4), how do we book Shinkansen trips? Can we reserve seats in advance, or do we need to wait until the Pass is activated? I’m concerned because Shinkansen tickets can sell out quickly, and we want to ensure we secure our seats.

4/ For daily commuting with the Japan Rail Pass, how do we use it? Is there a separate gate for checking in? Will we need to exchange it for another card when commuting between locations?

Thank you so much in advance for your help.