This madOS ROM is compatible with smartphones Vernee Apollo Lite and Apollo X. The latest 7.1.2 build must be flashed with SPFT before this custom ROM can be flashed.
Download madOS ROM and Recovery from xda DevDB or Mediafire
Download 8.1 OpenGapps nano or pico from xda DevDB or Mediafire
Now make a backup.
Now you can flash new mandatory TWRP for Oreo.
Boot to the new TWRP recovery
Now you need to make full Wipe mandatory
Install rom (optionally following by GAPPS if you use them)
Optional: go to: wipe — Advanced Wipe, tick ‘cache’ and klick ‘repair or change File System’ — change File System — F2FS — swipe to the right (hit back several times, and proceed the same way with ‘data’)
And last you need to reboot system