Below in the AnimGraph of our Animation Blueprint, we use the CCDIK node with the Effector Location being driven from the location of the button inside our Level. If the player is in range of the button and presses the corresponding key, we blend to the pose that uses the CCDIK node, causing the character to reach for the Effector Location (pressing the button).
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Below we assign the clavicle_l (left shoulder) as the Root Bone and the index_03_l (last digit on the left index finger) as the Tip Bone as our bone chain. We also define use the Rotation Limit Per Joints section to constrain how much rotation is applied to each bone.