Tearing is a property of the output from the GPU. The data takes time to send, and the GPU can be directed to send different data halfway through the process (or the memory it's in the process of sending can be modified, etc.). The display just shows what it's sent... it shows it as it receives it (CRT), or it buffers it up and draws it later (LCD), but if there's a tear, you'll see it just the same.

Screen tearing is, iirc from the gpu buffer only partially overwritten with the next frame when it's sent to the screen.

Tearing is, IIRC, a product of only part of the next frame being rendered when the refresh happens.

Obviously not, there is no memory inside the glass, and bandwidth is limited. LCD screens still scan in.

The difference is LCD keeps picture until told otherwise, whole picture is emitting light. CRT has limited phosphor persistence, there is only one point/pixel being lit at any given time.

https://www.youtube.com/watch?v=nCHgmCxGEzY