Consider the sequential circuit shown in the figure, where both flip-flops used are positive edge-triggered $$D$$ flip-flops.

The number of states in the state transition diagram of this circuit that have a transition back to the same state on some value of “in” is _____.

We want to design a synchronous counter that counts the sequence $$0-1-0-2-0-3$$ and then repeats. The minimum number of $$J-K$$ flip-flops required to implement this counter is _________.

Consider a 4-bit Johnson counter with an initial value of 0000. The counting sequence of this counter is

The minimum number of $$JK$$ flip-flops required to construct a synchronous counter with the count sequence $$\left( {0,0,1,1,2,2,3,3,0,0,...} \right)$$ is ____________.