Download the official for your operating system.
A custom recovery replaces the basic factory recovery menu, allowing you to flash custom operating systems. Team Win Recovery Project (TWRP) is the industry standard.
Every manufacturer is different.
the existing system, data, and cache (this deletes all your files). the Android 9.0 ROM zip file from an SD card. Install GApps
If you can tell me the , I can help you find the specific custom ROM for it. Check and update your Android version - Google Help upgrade android 4.4.2 to 9.0
If the device gets stuck on the boot animation for more than 20 minutes, boot back into TWRP, perform another factory reset (wipe Data/Cache), and re-flash the ROM.
Download the matching Android 9.0 Google Apps package (ARM or ARM64, depending on your phone's processor) from OpenGApps if you want access to the Google Play Store. 4. Unlock the Bootloader Download the official for your operating system
Install lightweight launchers like Nova Launcher or Lawnchair via APK mirror sites to mimic the visual style and app drawer of Android 9.0.
Use Google Backup or a PC to transfer photos, contacts, and data. Installing a new OS will likely wipe the device. Every manufacturer is different