djib695 installation of applications like Signal, Telegram, WhatsApp
THis can be done through some sort of app store (something like FDroid, Obtainium, or the Play Store) or through downloading the APK's directly from their websites or Github.
Signal APK: https://signal.org/android/apk/
Whatsapp APK: https://www.whatsapp.com/android/ (Click on package installer)
Telegram APK: https://telegram.org/android
One thing to note is that if you go through with the APK route instead of some other app store or APK downloader like Obtainium, is that you will not get updates for these apps, or even alerts that there is an update available. Telegram does seem to have an implementation for something like this, but I would much rather advise you to go through something like unobtainium so you can get all updates for your apps without relying on something like a central repo. Making sure you're always on the latest app version is important to prevent patched bugs and security vulnerabilities from compromising your device.
djib695 Camera blocking
This can be done by either denying an app camera permission when they ask for it, or by using the camera access toggle, which prevents all apps regardless of their permissions from accessing the camera.
djib695 implementation of a VPN
This can be done with any VPN app for android.
djib695 location blocking
Similar to the camera toggle, you can either deny an app permissions for your location when they ask for it, or just disable it from your quick access menu.
djib695 data reset as soon as the phone is connected to a computer
This is not implemented in GrapheneOS, as it would be highly destructive and easy to abuse. Also, it's way too vague of a feature and implementation.
djib695 Implementation of an unlocking code that deletes all data on the device
This is also not implemented in GrapheneOS. Also, what do you mean by "unlocking code"?