Husband and I are off to Japan in September. I have a few questions about using the JR Pass while we are there. I know we need to buy it before arriving. Once we are there and we activate it will I be able to reserve our seats on all the dates we want to travel? We will need to travel:

NRT - Hiroshima
Hiroshima - Kyoto
Kyoto - Tokyo
Tokyo - NRT

We are well traveled but have never been to Japan. Is the train systems easy to use?

Thank you in advance for your help.
Molly