In data grid, we have the option to set limit of number of rows we want to show at a time. Can we customize it for a data grid such that it initially shows 20 rows and gives option to expand to show more rows or something on the same lines? I know we have something like this in list view but i can only use a data grid so do we have a feasibility there?
No, this is defined design-time.
You can fake it by adding several datagrids, showing only the wanted one. But that is not good practice.