Fenix - I think what you’re seeing is ‘by design’ - the tools only affect the vertices. Two points make up a rectangle. Rotating them only changes their relation to each other around the circumference of a circle - i.e. gives a long thin rectangle to a short fat rectangle. If you want to rotate the whole bitmap, you need to use the rotate layer.
For the mirror tool, check the tool options dialog - there is a toggle box that will give you horizontal mirroring instead of vertical.
The rotate tool does not seem to make sense when rotating a rectangle. Instead of rotating the rectangle it changes the dimensions. I can’t think of a time that would be useful. From the above post it seems to rotate a rectangle you need to rotate the layer. I can’t figure out how to rotate a layer. How do you rotate a layer? Maybe the rotate tool needs to rotate layers?
To rotate a layer you need a Rotate Layer over the layer(s) you want to rotate. Just insert a Rotate layer (Caret Menu>Layer>New Layer>Transform>Rotate. You’ll see two ducks when select the rotate layer: A green one for the origin and a blue one for the angle. Try it by your self and experiment the results.
First time you use a Rotate layer maybe you can complain about the pixelation of the rotated objects. Don’t worry it would disappear when rendered.