No, that's not possible with this model.

I also had a missing one in the delivery. Digitec then told me they didn't have one and I ordered that one: https://amzn.eu/d/fDDFodo

Yes, that works without any problems. Really great screen, I have 4 of them mounted via Vesa.

Yes, the monitor has speakers, the sound that comes out is not enjoyable, but they work! For me, the speakers don't play a role because I use external studio monitoring speakers. But by setting up the monitor I have of course tested them briefly and I can say that they sound about as good as the speakers of a premium notebook.

According to the manufacturer, only an HDMI cable (and power cable, of course). https://www.philips.co.uk/c-p/275E2FAE_00/qhd-lcd-monitor