Reserving seats on shinkansen using JRP

I am wondering... if I arrive to Japan the 1th and the same day I exchange my JRP, which will start working from the 10th, can I already reserve seats on the shinkansens for the period of validity of my pass (from the 10th to the 16th)? Or have I to wait the pass becomes active and than I can reserve seats?

I am wondering... if I arrive to Japan the 1th and the same day I exchange my JRP, which will start working from the 10th, can I already reserve seats on the shinkansens for the period of validity of my pass (from the 10th to the 16th)?

yes

As long as you have the actual pass, you can reserve any valid trains you want for the dated on the pass. It doesn't matter if it's a week or two in the future.

You can exchange your voucher for the pass and make reservations at the same time. It's best to write down what trains/dates/times you want.

The lines at the Narita pass exchange office can get long, so you could be considerate of others and only get a few reservations, as, once you get the pass, you can easily make reservations at any JR Green Window or ticket office at any station.