TL-WA850RE can only provide your internet extender but it does not support POE. For the POE connection, you can also refer to this: https://www.tp-link.com/us/faq-167.html This is very useful...

It requires high network speed. How about when you watch online video? Certainly, we also need to make sure your home network is working properly.

There should be no upper limit but we can only see three cameras at the same time.

Just make sure you do go to the local region website and the FW will be suitable for your product. Since you are in UK and your model is Archer C7 V4.0, the link you provided is the right one to...

oh, you may try this beta FW: Archer C1200 (EU)_V2_180308(beta): http://support.tp-link.com/f/c67e6e765a/?dl=1 I met the same issue before and tp-link support provide this beta FW which solved my...

Is the FW the latest one? It's recommended to update the FW to the newest firstly.