Hi Dasaradhi,
Jitendra already mentioned most of the facts. SMP3 is mainly focusing on OData (pure REST is also possible). SMP3 in its basic installation does not include the MBO Runtime anymore, but you can install it as a separate stack (choose zip file during SMP3 installation). MBO apps which run on SUP 2.2 or SMP 2.3 should run (without modification) also on SMP3 MBO Runtime. Technically, the SMP3 MBO Runtime is (almost) the same than SMP 2.3 with latest service pack. There are no new MBO features on SMP3 MBO Runtime in comparison to SMP 2.3, only the SAP maintenance period is a little bit longer.
For new projects I do not recommend using the MBO approach when developing apps. For older or already existing apps it is mostly recommend to not migrate them to "new" SMP3, because of work effort, for migration scenarios check this blog entry:
http://scn.sap.com/people/marvin.hoffmann/blog/2013/11/25/supsmp-2x-vs-smp-30--migration-effort
If you want to develop a new app which needs real offline support (Offline Caching is supported now already) I suggest you to wait for the next SMP3 service pack which will come soon...
Regards
Marvin