the stage 3 selection interviews are far more in depth than at stage 1- you won't pass stage 3 if you aren't the right person- and its a dead cert that passing the personality questionnaire at stage 1 is a requirement.
to be honest very very very veyr few people fail the personality questionnaire- not sure when you do it now, but 6 months ago you had to pass stage 1 tests before doing the personality Q- and most of those people on here who pass the personality Q went to stage 2.
There's no point trying to blag it- there are so many questions that you will forget what you said for the earlier quesitons (they repeat a lot of the same type of question). I was told that they look for consistency rather a certain personality, so it will probably be better to give similar answers rather than get caught out!