Yes, you can change the project ownership by navigating to the "project settings".

While you can do association with the change, but you cannot convert a change into a project.
Currently, a 3-level hierarchy (epic or top task or sub-task) is present and this number cannot be modified
Yes, it's possible. More details here
Yes.
You will first need to add them as a new requester.
After you add the details of the new requester, make sure to enable project management for them.
Note : A project license is required for users who need access to project management

The following are the permissions that a project member can have:
Below are the notifications sent out:
Project Assigned
Project Reassigned
Project Completed
Project Archived
Project Rescheduled
Project Member Added
Project Member Removed
New Comment Added to Task
Task Dependency Added
Task Dependency Removed
All predecessor tasks are complete
Project Task Rescheduled
Project Task Reminder
Mentioned in a Task Comment
Added as Watcher to Task
To be able to remove a member from a project, please navigate to the project settings, and under members click on the particular member and you will have an option to remove that member.

This is currently not possible and you will have to create them separately.
The date of creation of the tasks influences whether it precedes or succeeds that task. Overlapping of the dates could be a reason for the same.