Yes, it works, you just need a quad hole to ISO adapter, so I was able to install it in my 9N without any problems.

Unfortunately, I couldn't find this information anywhere at the manufacturer's or on the web in general. With a bit of luck, someone else will answer your question.

What is very important is that the JVC is connected correctly. If you remove the ignition key, the unit should switch off but it still needs continuous power to maintain the settings. Using the original connector cable for the car you are using solves the problem. It is likely that you have connected all the power to the ignition switch and this will erase the programming.

It has an aux hole, it works with the iphone

Unfortunately, I couldn't find this information anywhere at the manufacturer's or on the web in general. With a bit of luck, someone else will answer your question.

Yes that should be the right form factor 👍

No, according to our information, no further accessories are required.

According to my own research, the Peugeot 307 CC should have a 2-Din installation slot so that the radio can be installed. If this is the case, then this should fit.

According to the manufacturer, only for charging the battery, Android is required for music playback: https://de.jvc.com/car-audio/2-din-autoradios/KW-R520E/ Otherwise connect the iOS device via 3.5mm cable.