"""""""""""""""How do you get to the flat command?""""""""""""

Using the edit frame. If you look in the screenshot I posted of it, you will see I circled the handle to the one side. If you grab that handle and drag it to the middle, you will get a "flat" snap, which means you have scaled everything in 1d to flat.

The trimming is supposed to work like it did for you. Just if you see it trim a bunch of weird stuff in multiple directions, you can refer to what I posted to give it a chance..


""""""""""""""How do you offset a curve that is on a surface on the same surface?""""""""""

The offset wont do a "stay on the surface" operation, but you could use projection to do this. Since you already have a curve, you can view it in one of the planar views, duplicate it (Use the flat again), move it over the amount you want, then project it onto the surface again.