Does the Messenger, peace and blessings be upon him, not appear to select awliya' (saints) for them to receive knowledge and supplications from him? If so, why is Tijani's prayer of "Jawharat al-Kamal", which he received from the Messenger, peace and blessings be upon him, in a dream, denounced?

There is no legal or rational evidence for the appearance of the Prophet, peace and blessings be upon him, to some Awliya (saints) and Aqtab (poles) for them to receive knowledge and supplication from him. Rather, this claim is an fabrication of the people of innovation, such as the Tijaniyya. The Sharia was perfected during the Prophet's lifetime, as confirmed by Allah's saying: "This day I have perfected for you your religion and completed My favor upon you and have approved for you Islam as religion." So, what was not a part of the religion then, is not a part of the religion today.