Many of these endpoints were scheduled for retirement in July and December of this year. Developers were NOT notified in advance that they would be abruptly shut down today.

I also believe this is a reaction to all the recent privacy issues that Facebook is facing. They identified Instagram as a huge risk for behavioral mining (it is) and abruptly shut down all features that can be used to analyze behavior and infringe on privacy at a large scale.

A deprecation is, normally, a notification (not the same thing as actually turning something off).

This was not a deprecation. They immediately and without prior announcement revoked access to many endpoints that had been scheduled for shutdown later this year and next year.

They already closed down everything in 2015 setting up a permission review system with very silly criteria.

Silly indeed. I applied for it twice, having submitted a screen recording explaining what I was using it for. They gave me partial API access, pretty useless functionality. Not what I needed which was clearly explained in the second video.

The application felt like I was begging. Not something I'd ever do again.

Yes. I had many web projects that were cut short by the requirement that you had to submit a video of a working app to get access to the API.