Question: In which season and episode is Gallifrey destroyed, or is it just a shocking new plot development for the new series?
Tiger Left, Tiger Right - S2-E6
Question: The episode first aired October 1964. How could a Ford Mustang be seen in the episode if that car wasn't available until April 1965?
Answer: Production vehicle models aren't in sync with the calendar year. The '65 Mustang began production in March 1964 and first sold in April 1964, before it was "introduced" the following year. I don't know which model was seen in the episode, but the 2+2 fastback was sold in September 1964. The 1964 film "Goldfinger" uses a 1965 Mustang as part of Ford's product placement. Basically, in the 1930's, FDR ordered automakers to release vehicles in the fall of the preceding calendar year "as a means of facilitating regularization of employment in the industry." Now, automakers can release new models as early as Jan 2 of the preceding year.
Answer: It was never destroyed on-screen; it was intact at the end of the TV movie, and destroyed by the start of the 2005 series. It was destroyed in the novel "The Ancestor Cell," but in a completely different manner to what happened in the series.
DaveJB