I tried updating to Sonoma from High Sierra on my MBP 2012 and it got hung on the boot screen. I tried many ways to get out of it. However nothing worked. I can safe boot and that's just about it. Can I atleast go back to high Sierra by creating a bootable USB with the downloaded dmg file? Thanks in advance
Use TransMac, which has a 15-day trial period and works flawlessly.
In the left pane, right click the USB Drive and select Format Disk for Mac
In the left pane, right click the USB Drive and select Restore with Disk Image
Point to your .dmg (or choose All Files to select an .iso) file and click Open.
It will take a few minutes depending on size of .dmg and speed of USB drive, but once done you can pop it into your mac, hold down the option key when turning on the mac and choose the USB drive.
TransMac worked for me, but first you need to partition your USB drive with GPT. It will not work if partitioned as MBR. diskpart on Windows can do this:
diskpart
DISKPART> list disk
(Find the disk number)
DISKPART> select disk 2
Disk 2 is now the selected disk.
DISKPART> clean
DiskPart succeeded in cleaning the disk.
DISKPART> convert gpt
DiskPart successfully converted the selected disk to GPT format.
DISKPART> create partition primary