question A any but most test have a cut off
question B there isnt one just dont smoke
and if u smoke lets say....1.5 grams in one week you will be clean in two weeks or less now where you get to haveing to wait 4-8 weeks is when u saturate your fat which happens when you try to exeed the amount you can carry in your blood at which point your not getting high anymore your just wasteing weed so stop after your high and your weed will last you alot longer