Probation after you are maxed out would serve no purpose, because there would be no mechanism available to enforce a violation of probation.
A plea can only be withdrawn under certain circumstances. That option may or may not be available to your friend. It will be harder to withdraw the plea after sentencing, so your friend better move fast.
Maybe your friend should retain a lawyer, instead of relying on the public defender he or she elected to go with?
Once a person gets the maximum jail, there can be no probation, since there would be no jail days left to impose if there were a violation of probation. So, some courts will give most of the jail, or almost all, but not all, so they can put a person on probation and still have jail days available if there is a violation of probation.
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Doubtful that court would do that. Once person serves max sentence the court no longer has leverage over the person to compel them to follow probation.