Off topic, can someone help me with the following on gitlab? Maybe I'm not searching with the right search parameters to get the right answers.

1. Who exactly is the assignee? When I'm working on a feature and raise a merge request, why am I given the option of selecting the assignee?

2. How can I cancel build pipelines when team members raise merge requests? I don't have a pipeline setup yet, but I don't want it to run in the first place (and fail)

3. Why is it that people who raise merge requests can approve their own request ? Is there a way to disable this? I would like to have people raise the merge request, but the ability to approve should lie with a few maintainers and developers.