It's possible to get released early from probation. Your attorney can assist you with filing a motion requesting early discharge. However, keep in mind that any probation violations will make it unlikely for you to be discharged early. Also it is helpful to have the support of your probation officer when making such a request. While each case varies, you may want to wait to file such a request until you've completed two-thirds of your probation. While it may be possible to get discharged earlier, it doesn't typically happen.
It depends on what you were charged with, but the faster you get the conditions of your probation done the faster you can get discharged. Like the above attormey said, it is up to the court.
Actually, the fastest way to get off probation is to execute your sentence. Of course, that involves serving jail or prison time, which not everyone wants to do.
It would more difficult to shorten a continuance for dismissal since the period of time is meant to assure you remain law abiding and is really the foundation of the agreement. A stay of imposition is a different story. One of the best ways to gain early discharge is to complete all of the probationary terms of the sentence....pay fines, finish community work service ect. Some counties do recommend discharge after completing 2/3 of the probationary term. You should not expect to be discharged after only completing 1 year if a 5 year probationary term. It would also be helpful to have a good reason for early discharge and the support of your probation officer.