28 days in Japan. Suica?

I plan on visiting various areas in Japan, and have booked an Air BNB in Tokyo to act sort of as a hub for my travels. I don't plan on staying there every night, but I figure it will be nice to leave all of my big stuff there.

Anyways, my trip is posted for April 30th, to May 28th. I was planning on flying into Tokyo, and then me and a friend were going to go to Sapporo for a few days, then I would come back to Tokyo, and start my trek to Nagoya, Hiroshima, Kyoto, and Osaka, as well as anywhere I can stop in between, and was planning on getting a 14 day pass. I had a few questions I had been looking for but could not find anything.

1. When purchasing a JR pass, does the "date of activation" have to be 100% accurate, or is it a general time to start? A follow up to that, let's say I am going to have it by the 30th, does that mean the start time is at the 30th, or does that mean that I can hold on to it, and then the timer won't start until I use it for the first time?

2. Along with the JR pass, I was thinking about getting a Suica pass to do my residential train work (on all non-JR lines). From what I understand the Suica pass will let me ride most any railways I need to get home. Is it worth it to get both, or should I just get tickets for local trains?

3. Besides the JR pass, is there anything else I need to have before entering Japan? I have my passport, I am getting my tickets soon, and my Air BnB is booked. How does the immigration process work?

Any information would be helpful. I realize that some of these questions might be broad or unspecific, so please ask me a question if something sounds weird. I just want to make sure I am doing everything right, since this is my first time travelling outside the US.

Thanks,
Trevor