Buddha supreme teacher

I wonder is it theoretically possible for an arahat to be a better teacher and know more than the previous historical Buddha?

I heard the saying to stand on the shoulders of giants do wonder if it is possible?
.what about each historicwl Buddha- are some better than others or all equal?

If an arahat can’t be better than our Gautama Buddha. Then why not?

Better of “What” between an arahat and your Gautama Buddha?