Roger Gracie explains to Bernardo Faria why the hand belongs on the middle of the chest inside closed guard - too high exposes the arm, too low weakens posture.
Posture first, then opening the guard from the knees or standing: pin the wrist, turn the knee into the hip, keep the leg vertical and slide their leg down it.
No-gi standing guard break: control the grips, walk the weight back, technical get-up while managing the legs, and keep the feet far enough away to avoid ankle sweeps.