Exposing unexposed cells & line thickness issues

I realized I needed to ad frames to the beginning of my sequence.
So I cut all the cells and pasted them back 20 frames.
I’ve since added key frames to the beginning of the timeline.
How do I expose the cells there that are unexposed without
affecting the exposure later on my timeline?
ALSO, I set my pencil maximum thickness to 3. But I’m
seeing varied thicknesses across my sequence, even things
on the same plane. Any ideas? (New to this)

For the exposure, you can select the range of frames to expose and go to the Cells window to choose the exposed drawing. This will only affect the selected frames.