I don't know exactly what you mean. But cashback campaigns do not apply to warranty extensions. And, for example, if the device would have to be under warranty and you would then receive a credit note (because a replacement is no longer possible), the warranty extension is also not refunded. So in both scenarios that I know of: No.
If you mean something else, please feel free to specify.
The volume depends on the level at which it runs. It is a bit loud at the highest level, but it only has to run for a short time at this level. In my opinion, it is very quiet on level 1, so it is not annoying. In automatic mode, it usually runs on level 1. I use the unit in combi mode
At tutti for 299 francs. https://www.tutti.ch/de/vi/st-gallen/haushalt/geraete-utensilien/luftreiniger-befeuchter-philips-2-in-1-kombi-3000-80m/39168349