I know one ziyarat in Behar Al Anwar which has this term "Nafsullah" for Amir Al Momeneen (as).

Kindly request if you can authenticate the chain and confirm if its Sahih. Also, if this Ziyarat proves to be from strong chain of narration then:

1. Wanted to know what is defined as NAFS with regards to NAFSULLAH.

2. Also, are both Prophet Mohammed (swa) & Imam Ali (as) NAFSULLAH?

3. If yes, what is the difference The Holy Prophet (swa) & Imam Ali (as) with respect to the position of NAFSULLAH?

With regard to the aforementioned visitation, it is a visit of unknown source, and there is no single evidence that it was issued by an infallible imam, so there is no consideration for what was mentioned in it.