Kaplan Tests are their own thing, so you need the kaplan answer keys for them...
Examkrakcers tests are also different, published by EK, with their own answer keys, thats why your answer keys from one company wont match up with another...
finally, AAMC tests are officially released actually administered MCats in the past, and thus these are the best to use for accurate score prediction.
In my personal opinion, AAMC is obviously the most realistic and best to use
Kaplan is great for biological sciences, useless for verbal, and difficult but good practice for physical sciences.
The only thing EK is good for is verbal.
