In Raven's Home S02E01-2,
Raven and Booker tell each other that they have visions.
From Raven's Home S02E03:
Booker: Why can't I tell people that I'm psychic?
Raven: You can. As long as you trust them. Like I trust Chelsea, and your dad.
When does Devon know Raven is psychic?
During That's So Raven S0XE0Y
Between finale and start of Raven's Home but excluding Cory in the House
Cory in the House (unlikely)
Sometime during Raven's Home (unlikely)
Never. Explanation in spoiler tag:
Raven trusts Devon but doesn't tell him. Trust is a necessary not sufficient condition for telling.