The person, whoever may be, if s/he can understand and predict something in horary (question), can herself/himself cast the Prashna Kundali as per the time when the question had arisen in their mind.
Or this is not allowed at all as per the doctrines of Horary?
why not, 100% allowed.
in other words, is the involvement of the two persons a must here?
I am going to tell you the general remedy to get rid of the bad effects of Ketu dosha or overcoming ketu dasha. To know the impact of Ketu in one's life, It is important to analyze the person's horoscope chart. First of all, Ketu is a natural malefic planet but not always brings bad to a person.
Ketu is often called as Mokshakaraka. As per Vimshottari dasha ...