You can change the color of a line by using the fill (press-and-hold) function but it's not possible to actually alter strokes.
It is possible to manipulate layer content with the Transform tool (in the Layers menu). That tool can be accessed by tapping on the layer with the content you want to move/resize, then to open the Layers menu, tap it again once it's outlined in orange, then choose Transform.
Hopefully that will help with some of the things you're wanting to do.
thanks for your prompt reply.
About your first answer it is perfect,
now I can change the colour of a
simple line, in the way that you showed
Whereas there is not any possibility
to draw a simple straight line and then,
in a second time, to curve it or to
change his dimension or position
without extend this operation for the
Correct. It's not yet possible in Draw to modify a single stroke. It is something that people would like to be able to do in the app, but I don't know what the plan is for incorporating that function.