You ask three separate questions. I will try to answer them in order.
The symptoms of carpal tunnel syndrome (CTS) are classically listed as numbness and tingling in the radial digits (the thumb, index finger, middle finger, and half of the ring finger). This can be followed by pain, aching in the same area. As the disorder progresses, the pain may radiate into the forearm or even the shoulder. The patient may also complain of being clumsy using the hand or having loss of grip strength. In some cases, the patient may actually have numbness in all of the digits, though that is not usual. (The small finger is supplied by a different nerve.)
Symptoms are often brought on by activities which require static grasping - holding a phone for a long time, grasping the steering wheel too tightly, holding a frying pain, and in cases where a person works with pliers, wrenches, etc. Vibration of the tools tends to make it worse.
Patients are often wakened from sleep with pain and/or numbness in the hands. This can sometimes be shaken out. As the disorder progresses, the symptoms tend to become persistent, with times without symptoms becoming less and less.
The reasons that patients wear splints at night, is to prevent them for bending the wrist down during sleep, as this is what compresses the median nerve in the carpal tunnel. When we sleep, we tend to curl up, bringing our hands up under our chin, and that bends the wrists down.
The carpal tunnel release (CTR) can be done through an open incision or through an endoscopic technique. But, as with any surgical procedure, there are risks. Overall, if the surgery is done for the right reason (that the person actually has CTS and the surgeon is not doing just in case), then it has a very high success rate, with very minimal problems.
But, the usual biggest problem, is that the symptoms do not go away. This, again, is usually because the diagnosis was not a firm one. There can also be problems with the wound, such as poor wound healing or infection. There could also be a surgical error and something gets injured. But, these are things that can happen with any surgery.
Overall the CTR is a very good surgery, with excellent results, and minimal problems. It stops the symptoms and returns the patient to a functional status.
How long it takes to get over the surgery, is hard to say. Everyone is different. But, in general most patients get back to everyday activities within a couple a weeks, and hard grasping activities in 4 to 6 weeks. Some patients have a problem called pillar pain, which is pain along the incision site, when pressure is applied to it. This can last quite a while, but not every patient gets it.