I currently have a F@ST3864V2 and need to be able to prevent my son from accessing internet at times. When I set time restrictions via the Optus wifi modem page (http://192.168.0.1 He manages to access somehow and then removes all the restrictions I have placed and if I change the wifi password he simply does a hard rest on the modem which then resets to the original password. Can someone please offer suggestions or advice.
A hard reset is not something you can stop. It is designed to reset everything to the factory setup.
On the plus side your son is showing initiative and savy etc. and that should serve him well in the future. On the minus side its pretty unacceptable behaviour.
My suggestion is that instead of a technical solution (which always has its limits) you should probably look to return it to a matter of trust. Kids doing the wrong thing is nothing new. Its just that with computers parents now look to a computer to solve the issue rather than themselves (not a judgement, just an observation)
So I'd suggest that if the modem is reset then all his electronic gadgets go away for a week. Explain this to him up front. His mobile, His school PC, His TV, His Nintendo etc.
This will no doubt cause you practical issues but it will cause him a lot more issues. The whole point of data access is it involves other people. Teachers, Mates, YouTube Celebs, etc. Let all of those other people remind him of how to behave instead of just trying to do it yourself.
After a week you can try again.
PS on the technical side there are much better options for controlling wifi. If you don't need an Optus landline then I'd suggest getting a Google Wifi/Nest to replace the modem. It has great inbuilt controls that you can access anytime via an android app an set access times on a device by device basis.