shift register confusion
After a while clock turns on, and immediately Q2 becomes D2 = 1, but since the clock is common to all flip flops, Q2 = 1 means D1 = 1, and since the clock is still on D1 SHOULD BE EQUAL TO Q1, so, D2 = Q2 = D1=Q1 = 1.

Flip-flops are edge-triggered.
The outputs do not change immediately. There is a propagation delay.
Timing diagram.
         ________________________________________________
D2    __|
               _______              ________
Clock ________|       |____________|        |____________
                _________________________________________
Q2    _________|
                                     ____________________
Q1    ______________________________|

Note the delay between the clock and the Qs turning on.