Travel advice for 12 day travel

I am looking for some travel advice for a first time trip (Mar 18th to 29th) travelling from:
-into Tokyo and there from 18th to 22nd,
-Hakone (22nd to 24th),
-Kyoto (24th to 27th),
-Hiroshima for a night and
-finishing in Osaka and flying home early on the 30th.

We have been told to get ourselves the JR pass for 14 days but I figured that the 7 day may be more suitable as we will only be making big moves from the 22nd to 29th. However, I am wondering if booking single trips may be cheaper and then today I read about regional rail passes. I am finding there to be alot of information out there but really unsure what would be the best and a bit uncertain with it being our first venture into Asia.

Any input or advice would be greatly appreciated!

We have been told to get ourselves the JR pass for 14 days
I am genuinely curious, who told you to buy a (nationwide) JR pass, and when? There was a huge price increase last October.

Yes it will be cheaper to buy tickets individually for Tokyo->Hakone->Kyoto.

For Kyoto->Hiroshima -> Osaka, the JR Kansai Hiroshima pass would be suitable.
https://www.westjr.co.jp/global/en/ticket/pass/kansai_hiroshima/

7 and 14 day JR nation wide pass won't pay off. Bad advice wherever you got it from.

5 day Hiroshina-Kansai pass will work for your Hiroshima leg of your itinerary.

One thing I would note with you itinerary, is for a first timer, you have very little time in Tokyo and Kyoto. You'll be disappointed with 2-3 full days at each only.

I would reduce your time elsewhere and add more time to Tokyo and Kyoto.

I disagree about the time in Tokyo and Kyoto.
On your first trip, it's impossible to have enough time to see everything in these places, not spending all the time in Tokyo and Kyoto allows to see more variety in what Japan has to offer.