[Answer]-Is there any way the access token created in iOS app can be used for our server to communicate with twitter & facebook

Sure, why not. Just establish a webservice which receives the newly created (“short-lived”) access token, exchanges them to long-lived ones and stores them in some database. After that you can use them for your server-side requests.

Have a look here:

• https://developers.facebook.com/docs/facebook-login/access-tokens/#extending