It really depends on the powder. If it's white and chunky (may not be) and has a numbing effect on the tongue, it's cocaine. If it's in crystal form, or powder with smaller crystals in it, it might be methamphetamine. Brown or tan powder is heroin. Also street drug test kits are available online, that turn a certain color depending on the drug.
Either Heroin or Mustard Powder
No. It's a supplement.
It's hash
well yes it does. because its a suspicious powder so the drug test will pick it up because its suspicious.
This section of a drug monograph would tell you if the drug is soluble in water.
yes
heroin
Heroin, mariquana, powder cocaine, etc...
DMT
Drug tests can not differentiate the means of taking a drug.
The scientific name of heroin is diacetylmorphine.
At your local grocery store or drug store.