"On'd oedd e?"
These tags are usually shortened in English - wasn't he? wasn't it? - rather than being left in their full form.
The problem with tag questions is that there are so many of them, used in so many different situations, and with so many dialect and register variations. At the moment, the course only covers a very few of them.
In developing the new version of the course we will decide how best to manage them at an introductory level.
All very confusing---- but at the risk of over-emphasising it, if you could include as much of the northern version of Welsh as possible because it is after all offered as a major alternative to the 'southern' version in the other courses.