have my Day1 next week the 23rd. Is that enough to get prepared for it.
Depends how much work you put in between now and then.
I heard the aptitude tests are pretty difficult so I want to cheat a little by downloading the practice tests from Skytest.
They're tricky for sure. SkyTest is very useful, many people I know have used it with varying levels of success on the day. I used it and got it so can only sing its praises. It's certainly not cheating, it's preparing, which is exactly what BA expect you to do.
Best of luck, BA is certainly not perfect but despite the moaning and groaning after recent events, it's still the best gig in town IMHO.