API update for app compatibility on older firmware versions
(extreme/unsafe method that blocks updates)
Before making extreme changes, take the following precautions:
1. Create a backup of the system partition and save it on the SD card, as root:
dd if=/dev/block/bootdevice/by-name/system of=/sdcard/system.img bs=2048
2. Place the RestoreSystem_signed.zip file on the sd card, next to system.img
adb push RestoreSystem_signed.zip /sdcard/
3. Permanently replace the recovery mode with a custom one (read the guide).
4. Now you can safely customize the system. To receive official updates you will need to restore everything by running the RestoreSystem_signed.zip file from Recovery. Once the process is complete, a system script will reinstall the stock version of the recovery on first boot.
Repeat this procedure every time you decide to start customizing only the system partition.
We as a free community were the first to implement WhatsApp on Nokia 8110 4G, exactly at the end of December 2018, when the firmware version of the device was v13, that is, before the official launch which took place in May, with the release of firmware 16 and KaiOS 2.5.1. This application was implemented thanks to the contribution of some users from India who provided us with the application to patch, so that it could also show the prefixes other than the Indian one, to make it work also in other countries.
At the time I, still lacking all current knowledge, was stuck at firmware version 12, due to a change in my system ROM that took place a few months earlier.
Users who had upgraded to v13 were able to use the app, while I, with my v12, was getting an error message with an infinite loading screen.
The same was true for all users with that firmware version or earlier.
In the end we discovered the origin of the problem were the old APIs, contained in the /system/kaios folder.
By replacing them with a more dated KaiOS device (for example Alcatel Cingular Flip 2) they "should" be able to use more recent services, in order not to be excluded from KaiOS software development, given the cases of total abandonment of certain companies towards their devices.
Download the more recent APIs from Nokia 8110 4G:
To install them you need to mount your system as root and replace the existing folder (do a backup of the existing one before) withe the extracted one:
After the restart, everything SHOULD work as expected, but I can't say for sure. I have also personally tested the APIs of other devices. There may also be incompatibilities of certain functions and applications, such as WhatsApp and Callscreen, but nothing of dangerous.