My Android phone prevents me from recording phone calls at the request of my carrier, even though it's totally legal for me to do so in my jurisdiction.
I'm not loving where this is all going.
Why not two people share a device, and when passed from one person to another, delete applications and install all apps and profiles from scratch using verified checksums saved on a blockchain. An OS which could do that is something like Nix. When passed to the previous person same thing, delete and install everything from scratch.
Using smartphones in a smart way, not a dumb way, like timesharing mainframes of the past. Same procedure could be applied to cars and other devices.
The actual SE filesystem available to a logged in user is pretty complicated. But the short story is that user-data is completely isolated. Presumably application binaries (which require digital signatures by default) are shared; although the "installed" state is not. Successive releases of Android have restricted access to any legacy "shared" data on the device (media folders particularly; pictures and video taken by the camera device have been strongly protected since Forever).
Verified checksums on a blockchain are only useful if they are verified by some provider who associates a blockchain ID with a real-world identity. Not sure what "blockchain" really adds. If anyone can create a blockchain ID, then "verification" doesn't really provide useful information.