Question: how to make ik fk switch?
Answer: Select the IK handle of the IK chain that you want to animate with FK. In the IK Solver Attributes, drag the Ik Blend slider to 0.000. ...  Select Animate > IK/FK Keys > Set IK/FK Key. ...  Deselect the IK handle. Select a joint in the IK chain, drag the current time indicator along the Time Slider and rotate the joint.