Is it possible for a superficial cavity to make my teeth so sensitive to even room temperature water and pain??

Unlikely: However, who says it is superficial. I have been surprised on a few occasions with decay that has developed below what looks like a small pit. The x-ray image will help determine the extent of the decay. You may have a bite issue causing the tooth to be extra sensitive, or receeding gums , exposing the root surface. See your Dentist and get it checked. Good Luck.

Probably not: However a small cavity in the enamel may open into a large infected area in the underlying dentin. Your symptoms seem to indicate something larger than a "superficial" lesion. Please see your Dentist for an examination and appropriate x-rays to determine your need for treatment.

It is possible: Decay from a small cavity that extends into the pulp can cause a sensitivity even to room temperature and toothache.

Not usually: Did your dentist diagnose it as superficial, or do you feel it is because it looks small? Tiny lesions in the enamel can extend quite deep.. like the "tip if the iceberg". Tooth may even have a fracture. Have it treated pronto.

Depends: Depends on a number of factors. Many "superficial" cavities extend much deeper when xrays are taken. See DDS ASAP.