Hi nolio,
1) Yes, that kind of glue can be removed easily, but still it will guarantee a stable hold
2) HomeGenie server is purely optional, just in case you want to add some leds, sensors, IR transceiving or such
3) you can use SSH for changing things, no need to remove the sd card
4) it was quite easy to add the power supply, but I had to use a small one, otherwise it won't fit
5) no particular reason, it's just the only extra raspi I had already in the house
Cheers,
g.