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Query 1: Regarding DataForm does not scrolling inside Relative layout.
We have analyzed your sample and suspect that you tried to set height for DataForm more than that of its parent so scrolling not working, we tried by setting height value less than its parent scrolling working fine.
Query 2: DataForm does not take HightRequest value
From your sample we found that you are set DataForm VerticalOptions to FillAndExpand. FillAndExpand will occupy spaces if there were empty spaces in parent view,hence there were spaces between DataForm and Label, If you set VerticalOptions to Fill, you can achieve your requirement.
We have modified your sample for the above two queries.
Query 3: How do I dynamically change a form size at runtime?
As you have set height for DataForm in your sample, we can set height dynamically. We have prepared a simple sample for the same.
We hope that this helps. Kindly revert us if you have any concern.
Subburaj Pandian V