GrapheneOS provides users with the ability to set a duress PIN/Password that will irreversibly wipe the device (along with any installed eSIMs) once entered anywhere where the device credentials are requested (on the lockscreen, along with any such prompt in the OS).
The wipe does not require a reboot and cannot be interrupted. It can be set up at Settings > Security > Duress Password in the owner profile. Both a duress PIN and password will need to be set to account for different profiles that may have different unlock methods.
Note that if the duress PIN/Password is the same as the actual unlock method, the actual unlock method always takes precedence, and therefore no wipe will occur.
Source: https://grapheneos.org/features#duress
What do you mean ? This has nothing to do with GrapheneOS in the first place (which by the way has been created in 2014. The article i linked refers to 2021).
Reverse engineering is a thing. It always has been. If every piece of closed source was a blackbox how can you explain exploitation ? How can bad actors exploit Windows, MacOS, CPU firmware and so on ? Your argument here is not practical. Also, why should Google put a backdoor inside a chip ? They already get every information they what directly from the people agreeing to use their software. So, why bother ? Moreover, every phone on the market has closed source firmware.