The judge is allowed to reject the plea deal. At which point the defendant can either withdraw their guilty plea and try their luck with a jury - or maintain it and accept whatever sentence the judge wants to impose-which could potentially be a lot harsher than what was agreed in the plea deal.

Unlikely relevant to this case, but judges are legally required to reject guilty pleas if they conclude that the defendant is being coerced, doesn’t understand what they are pleading to and the likely consequences of their plea, lacks competence to plea (due to severe mental illness/etc), or that the plea lacks a “factual basis” (e.g. if the conduct alleged by the prosecution and admitted by the defendant fails to legally constitute the elements of the crime; or if the judge has good reason to believe that the conduct in question never actually happened despite both prosecution and defence agreeing that it did)

On the last point-the prosecution is allowed to offer the defendant a plea deal for a lesser included offense, but not an unrelated crime that doesn’t correspond with what they are accused of doing-e.g. you can plead drug charges down to lesser drug charges, but you can’t plead drug charges down to possession of stolen goods if there is no evidence anything was actually stolen-in such a scenario the judge is supposed to reject the guilty plea

You don’t. But the judge can reject the plea deal that’s leading to the guilty plea.

Boeing isn’t pleading guilty in a vacuum - there’s a deal in place. Judge can reject that now, wait until after guilty plea and impose whatever sentence he wants (within law), or accept the deal as-is.

Judge needs to approve a plea deal. See Hunter's Biden case.