DFA which visit a specific state at least once
You can add the "have seen $r$" information as follows.

Based on the old DFA $A = (Q, \Sigma, \delta, q_0,F)$ construct a new one $A' = (Q', \Sigma, \delta', q'_0,F')$. State set of $A'$ equals $Q'=Q\times \{0,1\}$, which adds a bit to the original states.

In each step you mave along just like the original automaton, except when entering state $r$ when we set the bit to $1$.

Initial state $(q_0,0)$: initial, not seen $r$. Final states $F' = F \times\{1\}$: final and seen $r$.