Most efficient way to cover my 10 days

Hi
I will arrive in Japan late November for 10 days and the plan is as follows:
Day 1: arriving at narita and stay in Tokyo
Day 2 +4: tokyo
Day 4: mount Fuji
Day5: tokyo
Day 6+7+8+9: Osaka & Kyoto
Day 10: Himeji castle
Day 11: leave from kansai airport

• i will be using the 7 days pass so can i buy it online and activate later on?
• i want to make best use of the 7 days pass so i want to activate it on the 3rd day for a better use, good or bad idea?
• can i use it osaka-kyoto-himeji and to Kansai airport?

Thanks in advance