8 days Japan first time

Hi all,
I will be traveling to Japan for the first time in early June. I will have a JR 7 day pass. If I activate it on arrival on 2nd of June at narita airport, this will mean it will be valid from 2nd to 8th June, correct? Does this mean I can still use it for the whole day of 8th June or only until the time I first activated it (for eg. 9AM 2nd June to 9AM 8th June)?

I am traveling light and only have a medium backpack (less than 10kg) with me.

My itinerary so far is as follows:
2nd June Arrive Narita 730am. After collecting JR Pass when office opens, proceed to Nikko - Tokyo/Ueno to Nikko Station with JR pass via Utsunomiya.

3rd June - explore Nikko National Park area. Late evening, return to Tokyo. What time does evening rush hour begin and end? I will try to either leave early or later to avoid crowded trains. When is the last train leaving Nikko for Ueno via Utsunomiya? Or should I stay another night and catch an early morning train back to Tokyo? I must be back in Tokyo around 9am as I am meeting friends and we will go to Osaka together.

4th June - Osaka

5th June - Osaka - universal studios

6th June - Kyoto

7th June - daytrip to Hiroshima and Miyajima from Kyoto

8th June - Kyoto to Tokyo on early train. (since I activated my pass at narita let's say around 930AM, does it maen it expires on 930am 8th June, if so can I use the pass to get on a train back to Tokyo before 930AM?)

Please offer any tips or advice, appreciate it and thank you!
Joe