On another topic, They mentioned flipping tiles. Question is, how do you do it?

PUFFIE40

Press the "F" key.

To be more specific, first select a tile (or group of tiles), then, while holding it/them over the space where you place tiles, press F. The tiles are all now mirrored.
Do not flip tiles with events such as Destruct Scenery, Stomp Scenery, or Trigger Scenery on them, as it causes an access violation.

Also you CANNOT flip animations, also causes access violations.

Actually, you can flip animations.

But, I had to learn the hard way that flipped tiles with destruct scenery causes violations!