1) Yes. Apparently the tests are "easier" for younger people (quicker reactions/can adapt more quickly and other such psycho-babble reasons)
Young people aren't necessarily better at the aptitude tests though I'm afraid. The RAF initiated a "Pilot Sixth Form Sponsorship" where would be pilots took the full tests at 16/17, and if they then got through the tests and remainder of OASC, where offered £1000 towards their final year at school. Unfortunately the pass rate was very low on the aptitude, and many people included myself where dis-heartened. I have friends who went back a year/few years later and then passed. Rumour has it the RAF reviewed the sponsorship due to the low pass rate on the tests.