Hi! could it be possible that sleep deprivation and stress would delay voice change? my voice doesnt sound fully developed, more like 15 years old.

Yes: Sleep deprivation and stress can delay your body's natural development timeline.

Although stress: might be playing a part, I would encourage you to speak with a speech therapist. With training they can help men whose voices don't get deep enough and women whose voices don't shift to higher sound. Ask dr if there could be a medical reason as well. You may want to work with a psychologist to reduce stress and work on sleep issues, too.