"Be Yourself" - not your "idea" of what they want.
The above is the best advice on this thread.
Do your own thing. Be yourself. The guys making the selection are well trained and experienced. They know what they are looking for. If you try to 'act the part' you will be caught out.
If they decide they do not need you there is a fair chance you would not have fitted in or passed subsequent training courses.
In any case, good luck in your future whatever it may hold for you.