The following item is compatible with the Denon DP-400: Audio Technica ATN3600L.

No, no Bluetooth!

If you need spare parts, please contact our customer service. We can then make a request to the supplier :) => https://helpcenter.digitec.ch/hc/fr/requests/new

Not that I know of!

The Denon record player has a built-in preamplifier, so you can connect the record player to the two cinch connections of the Sonos port. In fact, you can connect it to any device that has a line-in input (with a jack, you only need a different cable). If you decide to use a different one, make sure that the preamplifier is built into the turntable or, alternatively, buy a separate one. Otherwise, you won't get enough signal for the Sonos port to be able to use it.

In this case, please contact our customer service directly so that your request can be checked. https://www.digitec.ch/de/information/contactinformation

Just needs the right cable. e.g. something like this Value Stereo jack - 2x Cinch (5m, Entry, 3.5mm jack, Cinch)

https://www.denon-hifi.ch/chg/product/hifi/turntable/dp400

No problem. The record player plays old and new vinyl (33s/45s/78s) without any problems.

The record player has a preamplifier according to the manufacturer's HP: "The integrated phono preamp provides an open, spacious soundstage that brings your vinyl collection to life while staying true to the original recording. You can also connect the turntable directly to an AV receiver, system component or integrated amplifier, even if these devices don't have their own phono input." Source: https://www.denon.de/de/product/hifi/turntable/dp400 This means it can be connected to "aux" or "line in". If you ever own an amplifier with a phono input, connect it via "phono". These preamplifiers are never as good as what is built into an amplifier behind a phono input.