I am not able to add a new page under the Start page as i couldn see a new page option in the more options menu. Trying to move a page into the start page, displays a msg saying "Content type(s) is(are) not allowed at the destination". My Start page inherits SitePageData and has only a MainBody property. Please advice what went wrong as I am new to CMS and Episerver.
Given that you don't see a new page option in the menu, probably suggests that you don't have the access rights to create pages.
Go to admin mode and check out the permissions for the roles you have on the start page.
If that's not it, it could be that someone set Availability to None for start page (which I doubt). Go to admin mode, find Start page under Content Types and see availability options.