jr pass

If you want to travel from Tokyo to see Kyoto/Nara/Osaka and Hiroshima within a week, then yes you will truly get your money's worth for a 7 day pass. Although if possible, spending more time on your trip would be far worth it - you simply can't cover all there is with just 3-4 days.
If you can, spend at least 2 days to see Kyoto, 1 day for Nara, and 1 day to see Hiroshima/Miyajima. For Osaka, since you are seeing Tokyo already, you can largely skip it during the daytime. But after the temples close in Kyoto around 5 PM, it is easy to zip over to Osaka to spend the evening. Dotonbori in Osaka is a must see place at night:

https://www.youtube.com/watch?v=COJ_MeXbeow

You can use the JR Pass on all JR train lines - the only real restriction you need to be aware of is that you can't use it on the fastest bullet trains, Nozomi and Mizuho. But other bullet train types will still get you there quickly. You MUST buy the exchange order for it before you arrive in Japan. Then when you are ready to start using it (even from Narita Airport) you can activate it immediately at a JR office, or choose another date to start using it. The time you choose to activate counts as day 1 to midnight. So if you activate it at 6PM your first "day" is just 6 hours.

While in Tokyo, you can also use it on the JR Yamanote Line within the city, which goes to many popular places. You can and should take a day trip from Tokyo to some other popular place, like Nikko or Kamakura as well.

Thank you so much
would consider your valuable opinion