1. You remove the covers on the back and it will allow you to screw it in place, screws come with the kit, but you can also get security screws if you wish.
2. Yes someone has got the AMG logo and loaded it. The boot animation files are at
https://mbworld.org/forums/attachme...-android-headunit-installed-bootanimation.zip
It is a bit tight to fit, but not that bad, and the W212 is a lot easier than the W207 unfortunately. Takes about an hour from start to finish to install once you have done it once.
On the hissing side, this usually means the cable is routing past something causing interference. I had it on one install I did where I went through the centre console past the gear lever. Re-routed it to go behind the carpet down the centre tunnel and into the cubby that way. Did mean extending it, but it eliminated the interference. Others I have done it on have been fine down the centre so not consistent. I did try a ground noise isolator which did work, but dropped the volume significantly. Re-routing worked much better.