Can plasma screen tilted will it damage the plasma screen?

yes.

most can tilt about 10 degrees back or forward, beyond that you're taking a big risk.

never, EVER, lay a plasma tv flat. Even if you're moving it and it's turned off.

The heavy glass can be de-laminated from the phosphors, blurring or ruining your picture.

If you really need to tilt your screen, the safest bet is an LCD.