You won't get advice on questions as it's against TSR guidelines to give anyone an advantage in exams or interviews.
The recruitment process is explained on the RAF Recruitment website. What I can say for PTI is that the Specialist Interview expects a high degree of confidence and communication; you won't just take part in sport, you'll be leading warm-ups, officiating a game, instructing others in sports skills as well as other physical tests.
What experience/quals do you have in playing and coaching sport?