Questions about BenQ TK800M

But this is a DLP projector that upscales 4K. Not a 4K projector like the one from Sony. There is no real 4K for this price.

I'm not sure exactly what you mean by your question. But if you're asking if the projector has built-in smart TV functionality, then the answer is no.

Yes, I have mounted the beamer on my ceiling. It works without problems with a suitable ceiling mount.

Of course that is possible - but only via HDMI. The other output is analogue jack 3.5 mm. It can also be looped through the home cinema surround system.

Google "replacement lamp BenQ TK800M". You will find various offers, both in Switzerland and from Germany with shipping in Switzerland. A naked original replacement lamp costs about 90 €. The installation in the module is tricky, the whole original module about 220 €, and it is easy to install. In addition, there are cheaper generics.