Lacquer can be removed with lacquer thinner, but that is a more agressive solvent than the alcohol used for shellac, use with care.

If you buy shellac in a can, try to get a fresh can as it has a shelf life as it is a natural product. That is why it's often sold in dry form. If you use old canned shellac it may not dry properly or hold up well.

If you use a water base polyurethane it can be cleaned up with soap and water as long as it hasn't dried.