Is there any option to control only the bandwidth of Guest Network in Archer C20? There's a Bandwidth Control option for only the guest network in my other TP-Link router which is TL-WR940N but I can'

The router randomly reboots 2-3 times/day. I tried using different power adapter with the same output rating but it doesn't solve the issue.

Is there no update routine for TP-Link midrange routers? Last Firmware update was on February 2018.