@utkarsh joshi
1000 (Q3, Q2, Q1, Q0) this is given in question
now you have taken initialy
1000 (which is right)
means after doing exor opration of Q3,Q2,Q0 =1 ,you put this value at the the position of Q3 and shifted the remaining bits and you got 1100
but according to figure it should be put at Q0 position