Weird FactsAfter looking at thousands of pictures and hundreds of Dbz episodes I've noticed some weird things.
After transforming to supersaiyan level one Goku never or very rarely wore his Martial Arts blue belt with the strands hanging.
After transforming to supersaiyan level one Goku never wore the sign that Master Roshi trained him on the front of his gi. He also stopped wearing the sign that King Kai trained him on his back.
After the Freeza saga Goku very very rarely used the kaioken technique. This might be the answer to #2
Goku wore more than one belt, while he was little he wore a black belt, in some of the Dragonball movies he wore a white belt, in Dbz he wore his blue belt, after transforming into a supersaiyan he wore a belt that had no tie.