Hi

I got a BB 8310 at&t unlocked and use it in India with Airtel as the carrier.

I installed facebook, twitter, linkedin and blackberry msgr on the handset but m not able to view any of them except linkedin application. Though m able to c all the application listed under the application option.

Is there anything I can do to use a blackberry to its full potential?

Do you have a BlackBerry Data Plan on your account?

Linkedin is a basic text application that uses your blackberry email to send and receive messages in full mode but has a basic limited text use also. it is also integrated into you contacts and calendar. I would suggest the reason it does work at all is the text part which is using the basic cell service.
As NJ stated you need a full Blackberry Data plan to make the others work.