I lost only my homepage changes - due to child theme

To turn on the revisions on page, edit the page and on top right click on Screens button. 

There select or check the box Revisions, now you have all previous edits there to to go back. 

If you lost your parent theme customization settings after activating the child theme, in that case you need to reactivate parent theme and use a plugin to download the customize settings so you can import them in child theme.