I am going to buy .com Domain so Can Anyone Please tell me Which Method I have to choose?
If you use Method 2 - it means that the domain is parked on our ns-servers (ns1.ucoz.net, ns2.ucoz.net) Subdomain and e-mail creation is available in Control panel of the website to which the domain is attached.
If you choose Method 3 - its management is in the domain Control panel (where you have purchased the domain)
It's a General Question So Hopefully I will get the Answer !
No, it is not. Everything connected with domains are in Additional Features board.