Legal Question in Criminal Law in Michigan

Depends on the underlying charges and the judge. He needs an attorney ASAP.

Probation may be extended with or without a jail term. You stated prison (must be felony for a possible prison sentence) if that is the case there are many factors to consider, sentencing guidelines etc. Your "friend" should have an attorney to minimize his consequences. I have had great success in this area. Feel free to contact me.

That it up to the judge. It will depend on the nature of the violation, if he has any previous violations, who the judge is, and if his probation can be extended. The judge could also revoke probation and re-sentence the defendant up the maximum amount permitted by law for the underlying offense. Probation violations are very serious for this reason. If he does not have an experienced criminal defense attorney on his side, now would be the time to get one.