Your question number 3 is excellent! The answer is covered in the radio play. While aboard the Tantive IV, Antilles actuates code EPSILON ACTUAL, a voice-override to 3PO and R2’s programming that programmes them to protect the princes at all costs. Lying and self-destruction are included. Princess Leia actuates EPSILON ACTUAL again when giving R2 the Death Star plans, and that’s why he becomes so focused on getting to Kenobi. It’s also why 3PO lies to Luke re knowledge of the princess.