Will denture cleaner tablets work for a plastic retainer?

Yes but make sure: They are both made of similar materials and denture cleaning tables will work on both. However, i would still verify this with the dentist who made you the retainer as different companies and different dental labs may use slightly different materials and you want to be absolutely sure that you will not do any damage to it.

Yes: If you mean a plastic retainer such as a vacuum formed retainer ala invisalign, yes it will help clean them. Be sure not to use hot water as it will distort the plastic. Also, do not clean these types of retainers with toothpaste, as they are abrasive and leave striations where bacteria can accumulate.

Yes: Scrub with toothpaste, then drop in the solution. Keeps it fresh and kills the bacteria. Good thinking!

Typically yes: First, call your orthodontist and ask what they recommend for the type of retainer that you have. Usually denture cleaner works well, but check first.