I have a Nokia G-2425G-A provided by my ISP(Airtel) which is ONT+Wireless Router. and also the settings like PPPoE configuration are locked, Can Anybody Help to unlock the settings
If it's not there, it's not supported.
With an OpenWrt intermediary you can do what you want:
LAN or WIFI < --- > LAN OpenWrt --- OpenWrt WAN < --- > Your FAI BOX
However, this will pose problems if the ISP-BOX is also used for Internet TV to a specific housing like at home in France because the ISP-BOX box must be connected directly to the housing whether it is LAN or WIFI
It can work otherwise but you have to use VLANs with managed HUBs
All Box's regardless of the ISP with us have completely hermetic firmwares !!!