Hi Srinivas,
7.31 is 7.4 with the capability of Hana as DB.
Most of the recent features were developed only for 7.31 and above, for example BCM (Broadcast Messages) which allows you as admin to send notification for specific users who has a specific roles or group.
SAP Fiori Launchpad on EP which is the current UX of SAP. (not available on 7.3).
Basically all of the new features since 7.31 SP11 exist only in 7.31 and above.
BR,
Saar