My monitor has 3 problems. Are they linked?

1. When I turn off the monitor with the power button, it turns off. But when I try to turn it on again with the power button, it doesn't turn back on. I need to unplug the power from the monitor for it to start again.

2. When I increase the brightness to 75%, the whole screen starts flickering fast. When I go up above 80%, it flickers even faster.

3. When my Mac puts the display to sleep, but I move my mouse to wake it up, the monitor doesn't wake up, and there is a green light flashing once every 3 seconds on the motherboard,

My monitor only turns on when I plug it to the computer for the FIRST time. Even then, it only works 20% of the time when I plug it in. I often have to unplug and replug 5 times before it starts.

Do you know what is causing each of these problems?

Are they all linked?

What components are at fault?

Thanks in advance