Dynamic Date Sicer

Hi Farmaan_1,
AFAIK, you can't have between slicer with relative date functionality. The max you can do is fix a start date which is usually an option for YTD/QTD/MTD defaults. But again, even in that case you need to update the slicer manually every year/quarter/month to fix the start date.

One work-around I can think of is having 2 buttons in the screen: One for relative date and one for custom date (between slicer). Default with last 6 month relative date so that data is only for last 6 months when user opens the dashboard. If the user want to select specific range, they can click on button saying custom date wherein between slicer appears and relative slicer disappears. 
In short, 2 buttons:
Button 1: Relative Date -> Relative date slicer
Button 2: Custom Date -> Between date slicer

Your requirement is a limitation in Power BI and I would suggest convincing the client for either relative slicer or above alternative where only an additional click is required.