Does pain from a blood clot in the arm spread to different parts of the arm or is the pain only felt in one spot on the arm?

I assume you mean blood clot in your vein, i.e. deep venous thrombosis. This condition usually doesn't cause significant pain, only a feeling of discomfort and occasionally local swelling distal to the clot. If the clot is in the artery, you will see the change of the skin distally along with severe pain and numbness. Clot in the arm's vein or artery is rare unless you have underlying disease.