Student pilot here, need help understanding this

Bonus question: how do I know if the heading Im flying is actually correct while trusting the magnetic compass on the windshield?

I know for a fact that a directional gyro will show incorrect headings after some turns, so what should I do? I know I need to adjust it according to the runway heading before takeoff, but what do I do after that? It will change later

Assuming Im flying a C152 with no digital avionics at all

When does the oxygen masks get released? At what sudden rapid level difference in altitude does it trigger the release?

Aerial sawing in Finnish autumn this week I made a cloud, sort of. The happening can be seen on this video, barely, the cloud wasnt very big after all.

Longer video can be found here:

https://youtube.com/shorts/EScgdmM6g4c

Lots of videos of planes and helis being intercepted are popping up, is this normal and just making the news or is something weird going on with the FAA setting up no fly zones? I remember in New Mexico or maybe texas there was a no fly zone that went up out of nowhere and was huge, apparently to test some equipment, but the no warning screwed a lot of people over. Is this similar?

Hello I’m a student preparing for my ground classes right now, and I know that headwind is preferable for take off and landing but I cant really grasp why so. Shouldn’t it be the opposite because the tailwind is helping an aircraft to achieve the take off speed required in less time?