The difference between Grafana v7 and Grafana v6

I would like to learn about panels that can be used with Grafana 6 series but not with Grafana 7 series.

Basically, I understand that the panels that can be used with Grafana 6 can be used with Grafana 7, but I would like to know information about the incompatible panels.

If you have any information, I would appreciate it if you could collaborate with us.

Thank you for your cooperation.