[When a Defect status can be changed by the developer / team?]

When a defect status can be changed by the developer/team.
Once defect is raised and test execution status is in-progress or once testing status is signed-off

Defect status change depends, what kind of statuses organization has. E.g. they can be New/Confirmed/Working/Fixed/Closed. In that case when dev starts to fix the defect he changes it to working. And when he has finished, it’s fixed. Every organization has own needs for defect statuses, and how the process goes, depends from those. I’ve been working at multiple organizations and I’ve seen almost as many different ways to do things.