What is the difference between a good deed (hasana) and a rank (daraja)? May Allah reward you.

A good deed (hasana) is the reward and recompense for a righteous act. It may also refer to the righteous act itself. A single good deed is multiplied tenfold, up to seven hundredfold, and to many more multiples. As for a "darajah" (degree/rank), it refers to a status or position, and these vary and are elevated by performing righteous deeds.