What causes numbness in feet and fingers.?

MANY things. Could be peripheral neuropathy. It could also be a reaction to a chemical in your house or a cleaning product. Carbon monoxide exposure, heavy metal exposure (lead, arsenic), vitamin deficiency, radiation exposure, and electrolye imbalances are just a few possible causes. See a doctor.
Depends. Loss of sensation in the far end of the extremities can be related to underlying medical diseases like diabetes and problems that affect blood supply to the limbs. Certain medications, including specific chemotherapeutic agents used to treat certain cancers have also been shown to cause peripheral nerve damage. A slipped disc in the spine can also cause sensory changes in specific patterns.