Slow down
Which machine do you have?
You can embroider on almost anything you could clamp into the machine (I was told that the toughest thing to embroider is a Karate belt).
Shoes would not be an issue.
Multiple colors, yes. Did I do it, No.
How many stitches, I do not know how much you can cram into 2x1 area?
Shoe size, as long you can clamp it
Miss-sew, I had to use Peggy's stitch eraser last night
Shoe tongue, Yes.
Material thickness, I still have to mess with my clamp, I need to bring it as down as possible to the sewing arm. Thickness should not be an issue. I had issues with this shoe when it would go from one material to a different one, you can see that it goes from suede to that puffy fabric.
Clamp is a home made