This is an example page where the scroll to top and automatic setting of the iframe height is implmented.
Please look at the source code to see how this works.

This is a simple div with a height of 600 px and a border of 2px.

If you click on the link below you come back to the same page but your parent page should scroll to the top.
Scroll down your page to see a result.

Link to this page

This a 2nd small div with id="iframe-second-div" I use as example how to hide an element in the iframe.