Step 1:
The moon changes its position in the sky regularly.
\[
\therefore \text{Chandrama is in motion}
\]
Thus, Assertion A is correct.
Step 2:
The statement says that whatever has motion is not changeable.
Step 3:
Motion itself implies change in position.
Therefore, the Reason contradicts the nature of motion and is incorrect.
Step 4:
Hence:
\[
\boxed{\text{Assertion A is correct but Reason R is incorrect}}
\]
Therefore, the correct answer is:
\[
\boxed{\text{(3)}}
\]