Not sure your topology and requirements, but maybe this video will be helpful for you: https://www.youtube.com/watch?v=7i17jvrIjD0

After reset, do you have internet when connecting to EAP's Wi-Fi? Usually you should have internet then. If you failed to log in, what error did you get? You can also try different browsers and...

Do you mean you don't want a router in your diagram? But switch doesn't have NAT function. I'm afraid only one switch won't let you have internet even if it has DHCP function. I'm not sure what will...

You can keep observing it. Maybe this time it's over once and for all?

Is your modem's LAN IP 192.168.100.1? Did you change the LAN IP of the router, 192.168.0.1? Make sure no IP conflict. Before you upgraded the firmware, did it work fine?

I think you can configure an ACL permit rule across VLANs. I only found the guidance in the UG:...