I think that should work, but I cannot speak from my own experience, as I only have one device in use. It is always possible that a neighbour has such a device in use. This would mean that it would also be within the 300 metre range...

We have used this battery: CoreParts Battery for Philips BabyPhone However, two wires on the connector of the new battery need to be swapped. This can be done with a fine screwdriver or a paper clip.

Hello, I haven't asked myself this question. I've been using it for 2 years now for my grandchildren and I've never had any problems (hacking or anything else).

Yes, the device transmits sounds. So the receiver transmits sounds that the baby makes. Alternatively, you can also use the receiver as a microphone and say something to the baby. We never use the latter, as it is probably rather scary for the baby ;)

The more expensive one has a much better display, temperature display and other setting options.

Yes, does not require WLAN.

So, according to my research https://www.philips.ch/c-p/SCD843_26/avent-baby-monitor-digitales-video-babyphone is probably a minimally better variant, a few more features, larger screen, night light etc., read through the specs. the cheaper version can be found here https://www.philips.ch/c-p/SCD833_26/avent-baby-monitor-digitales-video-babyphone

Same for us: USB socket was defective very soon...

The camera unit has no built in battery. https://www.philips.ch/c-p/SCD833_26/avent-baby-monitor-digitales-video-babyphone Akku- und netzbetriebene Baby-Einheit: nur Netzbetrieb Battery and mains operated baby unit: mains operation only

No. the model Philips AVENT SCD833/26 has NO room temperature. The model Philips AVENT SCD630/26 has room temperature (not sure they still sell this model).

Yes, I ordered a clamp to fix the camera. You can find them on the internet (AliExpress)