I have a Mid 2012 MacBook Pro with 512 GB hard drive which dual boots along with macOS Sierra.
I have converted macOS Mojave partition to APFS from Mac OS Extended (Journaled).
When attempting to install macOS Mojave 10.14.4 update, this screen stays for a while and then system restarts to back to macOS Sierra:
What is going wrong and how do I resolve the issue?
Your 512GB HD is a SSD drive right? APFS works only on SSD drives. (except for the Fusion drives)
The title of your question says: update macOS Mojave 10.14.2 to 10.4.4 => I think you meant 10.14.4 no? So, do you really need your system to have that dual boot thingy? Otherwise, I would recommend you to wipe you hard drive completely and entirely, but you'll loose everything. (that's why you have your backups up to date :-) I hope) Once your drive is empty, start the installation of macOS Mojave from a USB thumb drive?!
Before doing all that, if your system is still working, first create a Bootable USB thumb drive with the macOS Mojave installation on it.
Don't forget that wiping your hard drive will WIPE all your data!
