Can I do a u-turn on a blocked off road?
What do you think will happen if you do that?
I'll be arrested and put in prison.
It is good that you consider what could happen. You could get arrested or put in prison for driving like that. You could also get hurt.
I wish that wasn't the case.
I know doing a U-turn may be beneficial in some situations. But you should acknowledge the potential danger in making an illegal U-turn. The time it would save you is not worth the potential issues that could cause.