Freshwater will not kill red bugs. Lugols will not kill red bugs. Revive will not kill red bugs.
Interceptor will.
You do not need to treat the entire system necessarily either. If you are buying a new piece that has red bugs, treating it in a QT or at least dipping it will work.
If you already have placed the piece into your display, then yes, you would need to do a full tank treatment.
Call a vet and tell them what you are using it for. Be honest. It took me about five vets before I found one willing to prescribe an "off-label use" prescription. Now whenever I need interceptor, I just go there and tell them it is for my tank. No questions asked, they just print an off-label use sticker and away I go.