Incompetence is way more likely than intentional sabotage. It was probably just some guy in a suit demanding that they have everything that looks secure so it's not a repeat of the NDS, while giving no time to actually implement anything properly.

The button combination with a closed hinge one is all but confirmed to be deliberate. To my understanding it's meant to be used in Nintendo repair centres to flash a new firmware for refurbished devices. Of course not described as such to repair centre employees, but that was the intended usecase.

Unlikely. It's very difficult to write vulnerabilities that won't immediately be detected by coworkers, who will rightfully implicate you as adding backdoors to the firmware.

The vast majority of software developers are not Freedom-loving Stallmanites like we[0] are. In an economic system in which only scarce things are valuable, moral opposition to enforcing artificial scarcity melts away very quickly, at least in the hearts of the people who make the software. They don't have to be fully on board with the DRM agenda either, they just have to have enough moral indifference to show up to work that day and write the software that does the thing their boss asked for.

[0] To be clear, I think RMS is a terrible person, I just happen to agree with him that proprietary software and the DRM that protects it is harmful.

Most likely none. I doubt any developer working on this intentionally created a security flaw and snuck it in under the radar. Much more likely these are all fuckups caused by the top brass requiring much more security for their devices to "protect" themselves from piracy build by developers who didn't have experience in hardware security.

That is what I thought, too. (There are probably more than one people working on it and some people want to do some of such things deliberately) At least some of the things might be deliberate (such as the working of the hidden service mode); others probably aren't.