Re: Basler Mietvertrag and Basler Hausordnung
Giving notice by registered mail is the norm. Three months is the norm, but you need to look at the details of your contract to be sure. It is from end of month typically, so you need to notify a few days before, to meet the deadline or get stuck paying for a whole other month.
Sorry do not have the docs you mention.
Not having a receipt for deposit is a bit worrying, but maybe you have a record of the bank transfer. Hope you did not give cash.
Vacating 1 week in advance seems a bit harsh, but this could be stated in your contract. Usually a the day of handover, everything is inspected, but in your intestest to perhaps do a bit in advance if you anticipate problems.