Can you turn Adderall to crystal meth?

No, you can't. Methamphetamine is chemically identical to amphetamine, except for the addition of a hydrogen molecule in methamphetamine's chemical makeup. They're 2 totally different substances (though they have very similar effects). The reason methamphetamine is said to be "stronger" is because the addition of this hydrogen molecule increases the bioavailability of the amphetamine in your body (i.e. more is absorbed, therefore reaction is stronger). In addition, the presence of this hydrogen molecule allows the methamphetamine to cross the blood-brain barrier faster and with more success. Basically, to answer your question, no you can't make meth with Adderall.