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Nothing will prevent him from wiping your drive if he has physical access to your device.
Physical access access to internal storage.
A locked case to stop tampering with drives and and a password protected BIOS/UEFI with a boot order that skips removable media should prevent OS installation (as long as your motherboard doesn’t have a reset button on the back faceplate too).
That only prevents phone connectivity over WiFi. Turning off WiFi and using mobile data bypasses it. Using offline applications and games (or even Plex/Jellyfin etc) can bypass it too.
Family link does more than stop internet access at certain times, it allows setting usage limits by device and by app.