I would like a device to be able to connect to my network but not access the whole internet, 24-7.
 

1. I tried the block option which adds it to the blacklist and the device is still accessible but then on reboot the router is refusing to assign an IP. Clearly this is an attempt at a full network block option.
2. I tried creating a parental control group in the mobile tether app but I can only block the group for one day. I also tried to to create a bedtime for this group but this is limited to 12hours. Blocking specific sites is also not an option.
    

• Firmware page telling me it is up to date.
• Latest tether app

As far as I can tell your latest firmware does not support "blocking the internet" and only has a selection of inadequate workarounds? I have yet to try assigning a static IP on the device and using your full network block option, this may possibly be the only option to fully work around this issue.