es, you can update your old android phone too. Even if it no longer gets any new updates from the manufacturer. For this, you will need to get your hands on the custom ROM. Custom ROMs unlock the bootloader option and there are risks in the process so, proceed with caution. Custom ROM can also damage your phone. To update your old android phone, do these:  -Unseal the Bootloader.  -Launch a custom recovery -Make a backup of your existing android OS -Then flash the custom ROM and then google apps