What will happen if I initially set J=K=Clk=1 in this circuit?
The output of the flip-flop depends on the previous output. When J=K=1, the output(Q) of the flip flop toggles. That is, if the previous output was 1, the output will now be 0 and vice versa.

The state of Q-bar is always opposite of state of  Q.

Do verify my answer. You will be clear.