1- One does not have to be a Mujtahid or a very high ranking, pious Shia to be qualified to return. As long as this person has a complete belief, his belief is solid and firm, and does good deeds (fulfills all obligation, and if he sins he repents) then he would be qualified. So if he recites this Du’a 40 days he will have the honor to return.
2- Yes it is recited after Fajr. You don’t have to do it every year, but if you do, it increases your chances of being firm and having this honor.