Denon AMP system that I use wired speakers with TV

OK, that's a lot of questions.

1) Can I pair with my denon amp
With what?

2) would the connect work?
Assuming you have some line level input/outputs on your Denon, like a spare Tape input/output, your could use a CONNECT to feed your Denon receiver with all data from the Sonos ecosystem.

3) can I listen to say you tube from my smart tv
You could conceivably use the stereo line in on the CONNECT with your TV, the CONNECT has a single RCA analog line in, which does incur a minimum of 75ms delay, depending on settings, sometimes more. This makes some people uncomfortable with lipsync, it doesn't bother others. Most people use the designed for TV PLAYBAR or PLAYBASE, which has an optical connection to the TV, for low latency, which does away with most lipsync issues.

4) listen to a Sonos speaker in another room also
Yes, in a Sonos system, you can assign a stream to individual speaker "rooms". The don't have to be all playing the same thing. I often have one stream going on in my bedroom and bathroom, and another in my kitchen.

5) The Sonos One is the speaker with Alexa. The PLAY:1 is roughly the same form factor, but without Alexa, or a microphone. If it were me, I'd be purchasing a Sonos One, as it is more "future proof", having been designed and manufactured much more recently.

Hope this answers your questions.

Thank you for your reply. I have no idea why I didn’t read proof the above before I posted it. I think I got excited.

I have just bought two Sonos One speakers. Currently one in the hallway and one in the bedroom. I have my denon amp with wired speakerS in my living room. I am looking to put a speaker in the bathroom, be it a Sonos One just or a wired ceiling speaker put in.

With the connect or connect amp is it possible to setup more than one set of speakers.

One option is too wire up the ceiling speaker with the denon amp and play sound throught that. And then use the connect to also join up with spotify on my phone with the sound coming through my denon amp and through the wired speakers.

The CONNECT is a device that you can connect to your current receiver and get data back and forth, i.e. you can get the Sonos streams in to the receiver and out through the speakers on your receiver. They would be in sync with your other Sonos speakers in that case. You could also put the music from your receiver in to the CONNECT, so it would be sent throughout the Sonos ecosystem. Howevevr, there's a slight delay in processing that music, which means that all of the Sonos speakers would be in sync, but not with the speakers on the receiver. The lowest amount of delay is about 75ms, but depending on various factors, it can be more. This might not be an issue, especially if you can't hear both the Sonos speakers and the receiver's speakers at the same time, i.e. they're in different rooms.

Now, will the CONNECT:AMP drive more than one set of speakers? I'd recommend that you read this:

https://sonos.custhelp.com/app/answers/detail/a_id/269/kw/Connect:%20AMp%20speakers/