Back in the '70s, General Electric was marketing a Numerical Control (now called CNC) system made up almost entirely of NOR gates. By connecting them in various configurations, almost all functions of the control was accomplished. The hardest part of working on the machine was that GE used Negative Logic. It was hard to bounce between other controls that used Positive Logic and the GE due to that. They called the control the MARK CENTURY control.

 

Which gates in your diagram are sequential? All I see are 2 OR, 2 AND, and 2 NOT/inverter gates, no sequential logic there...

They may be arranged in such a way as to become a sequential component, but it is made of combinational parts.

I see that Q and Q` (outputs) are connected as inputs, isn't this sequential?

 

I see that Q and Q` (outputs) are connected as inputs, isn't this sequential?

Again, the gates themselves are combinational. It is their configuration (how they are connected) that creates the sequential aspect of the overall device.