How many days does it take for an oyster mushroom to grow and how can one recognise a poisonous mushroom.?

To answer your second question, there is no universal way to recognize a poisonous mushroom without actually feeding it to someone or something, or running chemical yses. The only way to distinguish poisonous mushrooms from nonpoisonous mushrooms is by studying mushrooms on a case by case basis, taxon by taxon. Bottom line is that you just need to study mycology.