salvia doesn't show up on drug tests
You don't; that's the whole reason for the drug screen.
if the pres is covering the drug in your body
No
You cant.
smoke more weed
No, adderall will show up on drug tests as positive for amphetamines.
No, methocarbamol is just a muscle relaxer, and are not generally on a drug screen, never heard of muscle relaxers showing up on drug screen, at least not on mine.
You cant, they show up differently on a drug screen.
You have prescription speed in you, no you will not pass a drug test. But, the fact it is legally prescribed to you won't make a negative difference in the outcome of failing the drug test.
Don't use drugs
About a gallon or 2
I hope not.