I am planning to upgrade my wife's Galaxy Ace II from 4.1.2 (the latest official firmware offered by Samsung, installed via Kies) to 4.4.4, which is available via http://novafusion.pl/downloads/ as an unofficial CyanogenMod 11.0 variant. I have tried to gather as much information as possible, but some things are not clear yet. I am seeking short, precise, technical answers; there are enough "10 steps for ... your phone" out there already. ;-)
I know what rooting means, but apparently it is not always necessary in order to install a custom ROM? (This seems to differ from Jailbreaks on iPhones.)
However, I probably have to "unlock the bootloader" in order to make the phone accept a firmware that is not signed by Samsung? (I understood that this is what "unlocking" the bootloader means.)
If I understood correctly, the (/a) recovery mode is always available and mainly offers the features to a) wipe the data partition, b) wipe a cache partition (which seems to be hidden from the UI, so I did not know about it before), or c) install an update.zip from an SD card. Apparently, there are more advanced custom recovery ROMs/firmwares out there, too, which is probably analogous to installing Grub instead of Windows' default bootloader. But do I need no install a custom recovery ROM, too? (Why) Is that recommended?