How long will a digital nerve block stay numb?

Nerve block. How long it lasts, depends on the drug used and whether or not there is an additional agent such as epinephrine. The amount of drug used is imoirtant too. Other factors such as metabolism, how long your body gets rid of the drug, circulation and concurrent medical and neurological condiitons all factor in. A simple digital block with plain 1% lidocaine in my hands usually lasts 1-2 hours.
Maybe longer. If no return of sensation in 36 hrs notify surgeon. There is a new local out there now called Exparel that can last 72 or more hours. They should be able to tell you if that's the case.
It depends on. The type of local anesthetic used, but most blocks of this type have worn off by 12-18 hours. Some wear off more quickly, though. Again, it depends on the type of anesthetic medication injected.
2 to 6 h. Depending on the medication used, Lidocaine 1 or 2%, bipuvacaine. 5% should resolve in that amount of time.