information about JR Pass

Hi there, I'm going to visit Japan with my parents, and was actually considering about JR Pass. however there are some questions i would like to ask about JR Pass, please kindly help me.

1) if i purchase a 7 days JR Pass, do i get to travel unlimitedly with shinkanshen? And i read that even if i buy JR Pass i still need to make a reservation for Tokaido line. How and where should i make this reservation?

2) Does JR Pass covers the tokyo metro? or should i buy another pass?

3) Once i buy the JR Pass, how do i activate it in narita?

4) How do i use this Pass? is it like a ticket that i just tap into the machine or i need to retrieve it for another ticket everytime i want to use it?

Thankyou in advance :)