you can download the current release from
Download Windows 10 Insider Preview ISO - Microsoft Windows
My only guess is that the windows update system was going off of its cached updates and had not updated to reflect the new build availability when you were on windows 8 still. As far as upgrading from 10130 I believe there is a hard lock in place to prevent you from upgrading the build more then once within a 24hr period. The system still is updating and installing patches a few hours after you log in to a new build and they are trying to prevent you from upgrading to newer code on top of the updating and risk breaking things.
The app issues MAY be due to tpm. The windows system uses this for security in quite a few places to include the store. When you upgraded the build this also updates the certificates and settings in the tpm but I believe this does not roll back when you downgrade. You will need to load tpm.msc to reset the tpm either by entering that in at the search window or adding the snapin on the mmc console.