Harry Potter: Did you know, sir? Then?
Albus Dumbledore: Did I know that I just met the most dangerous dark wizard of all time? No.
When Harry is kneeling beside Dumbledore's body, at the foot of the Astronomy Tower, Ginny joins Harry and holds him at his left side (viewer's right). In the last close-up of Professor Dumbledore's face, Harry is visible in the background with a space to his left and Ginny is now gone. That same angle was shown before Ginny joined Harry.
Young Tom Riddle is played by newcomer Hero Fiennes-Tiffin, who is the nephew of Ralph Fiennes, the actor who plays Lord Voldemort, aka Tom Riddle.