I want to know the limitations of this GSM module, means how much sms can i maximum send and receive using this module per minute. I am planning to use it along with the RaspberryPi.
Your questioning the GSM 900 module aims at the wrong part of the delivery food chain.
The real imitation is 'always' the carrier accepting the text message. If you expect 1 message per 5 seconds you should never be disappointed and if you try more than 1 message every second you will surely find messages failing. The point at which you experience failure will depend on the buffering/caching setup by the sms gateway / carrier.