Not true. If your project does not compete with your employer, you do not use their resources, and you do not build it on their time, it is yours. This it the case in California. That doesn't work well at a FAANG because they have their hand in so many pots it is easy to compete with them. Anywhere else, just work on something not related to your work. I'm in security and build in AI.

Incorrect. Without going into all the nitty gritty, even a lot of FAANG companies have explicit moonlighting policies that are fairly permissible.

At the one I am at now, you can get a written sign off from legal before you even start your side project, where they agree that all rights to the side project belong to you. You have to apply for each project individually, but the form is online, just a few fields, and is commonly approved (as long as it isnt a legitimate conflict of interest). I don't mind the process, because each time it nets me an official signed paper that explicitly states that my employer has no rights to my side project.

This is only situationally true, both in terms of employment contract and jurisdiction.

Rule #1: don't listen to sweeping statements about law on HN.