I see a number in &menu_id, how can I traduce this number to a valid string id? And I want to know the id of a parent menu, which I can't click (For example: Purchase->Configuration)

You could probably temporarily modify the ir.ui.menu tree view to include ID and parent id? This should allow you to get the id from menu items in settings. As for the string id not sure what you are asking - are you talking about the full path / complete name?

I am asking for the complete name, for example: id="menu_fleet_reporting"

Ok then. Well for complete name it has the label of full path in the model. This is visible on the menu item configuration form.

Not sure if you will need to replace "\" and spaces with underscores?