The pen that created the product page must have copied the data from the normal 6s. The iPhone 6s Plus does indeed have a 5.5" display.

It was an offer for a new product, but can no longer be ordered due to lack of availability.

I would not buy this iPhone. It is completely outdated and it is not possible to install the latest iOS version. Various apps already don't work on the iPhone 6s.

The goods offered in our online shop are new goods. Used items have their own category. The goods are purchased from a supplier and sold by Galaxus. Used products are explicitly marked in the online shop in the "Buy used" category.

Your provider (Swisscom, Sunrise, Salt, etc.) should be able to give you the sim card with the same number in the small size in the shop. Just ask there

We set our prices of products depending on the respective purchase price. Since the rose gold phone is a lot more expensive to buy, this is reflected in the selling price.

Why not, it may just be that you have to have the SIM tamped to fit first, as this iPhone is operated with nano SIM cards. Source: https://support.apple.com/en-us/HT202645

Various suppliers / external warehouse

Probably Digitec (unlike Apple) has not yet adjusted the prices downwards after the presentation of the new iPhone 7.

Yes the sales tax is already included (fyi it is 8%)

The FM receiver is there, but not connected to the rest of the phone. For whatever reason.