Honestly, 99% of the time people are doing it wrong. People are either too strict with it or too "loosey goosey" with it.
*EDIT* It doesn't have to be correct, it just has to work for the people on the team. If it works, then use it, if it doesn't then change it. That's agile.
If people can only ever get into the goldilocks 'not too strict, not too loose zone' 1% of the time, then it the process is by default not fit for purpose in almost any circumstance.
Likely the 1% of the time it works is the rare case that you have a small and exceptional team working together, in which case the project management methodology is unlikely the reason they are working well.
You don't have to, just find what works for your team and use it. It may not be perfect or exactly how it is supposed to be but if it works then use it.
No, they need to come up with that on their own. What exactly "wrong" means? And why do you think you know it better than them? What if they find some better way that you didn't know about? Agile says that it needs to be sustainable also for the sponsors. Show the team that if the sponsor isn't able to sustain the next sprint, there won't be a next sprint. The process is up to them.
*EDIT* It doesn't have to be correct, it just has to work for the people on the team. If it works, then use it, if it doesn't then change it. That's agile.