Should I buy JR pass before the price hike in Oct 23?

Daniel-san konnichiwa,

Three of us are going to travel in Dec 2023. Currently we are in Indonesia.
This is our itinerary:

Dec 15 Tokyo - Yokohama
Dec 17 Yokohama - Hakone
Dec 20 Hakone - Nagoya
Dec 24 Nagoya - Kyoto
Dec 27 Kyoto - Osaka
Dec 31 Osaka - Tokyo

My questions are:

1. If I buy the the JR pass in Oct before the price hike, can I still use it until Dec 31? Because that's the longest trip back from Osaka to Tokyo. I'm worried the JR pass would expire before I can use it on Dec 31.

2. Can you give me suggestion as to how many days of JR pass I should buy and starting from date or city should I use it from to make the purchase worth it?

Arigato gozaimasu