Good morning,
what NetWeaver release are we talking about?
For 1., you cannot do this for Netweaver releases 7.1 and lower (Refresh use case).
If your NetWeaver basis is 7.1 and higher you can follow your approach but it's
not necessary to uninstall the database (it will be just refreshed with the data of PROD).
In case of 2., it's related to 1. (Refresh possible, yes/no). But more clarity we'll have once
I checked the sapinst_dev.log.
Best regards,
Hendrik