10 Days Trip with 7 Days JR Pass

Hello! I am travelling to Japan with 2 other people from 19th - 29th March. I was wondering when should we start activating our JR pass or is there any alternative ways for travelling when our JR pass expires.
We will be arriving at Narita airport and will travel straight to Osaka and reside there for a total of 5 days. During that 5 days, we will be exploring around Kyoto and Osaka area. After that, we will come straight back to Tokyo for another 5 days which we will explore the area in Tokyo and also area nearby Tokyo and then go straight to the airport on the last day. May I know:

• When is the best day to activate our JR pass?
• Is there any alternative methods of travelling when our JR pass expires?
• Should we start out JR pass from the first day or from the third day onwards?
• Is there any other recommendations?

Thank you!