A bootloader is the low-level software that runs before your operating system (Android) starts. It tells the phone which kernel to load. When locked, it verifies digital signatures of the OS; if you try to load unofficial software, the phone refuses to boot.
The G4 overheats. After unlocking, install and then the Thermal Mod for G4 (available on XDA). This adjusts the thermal throttling values to prevent the bootloop trigger. lg g4 unlock bootloader
For most models, users must now rely on unofficial exploits or community-developed tools like the UsU (Unlock any LG G4 device) method found on XDA Forums Carrier Exceptions: Some variants, specifically the T-Mobile H811 A bootloader is the low-level software that runs
Gather these items before you type a single command: lg g4 unlock bootloader