u/justwatchthefire

The applications is actually going back beyond grandparents, the key is proving an unbroken documentary chain connecting each generation to the Canadian ancestor. The further back it goes, the harder it gets in practice, as it can get difficult to locate the documents needed to prove the Canadian citizenship of the ancestor.

I would really recommend looking into professional help if you are dealing with a complex multi-generational case, as it makes a big difference having someone who knows exactly what IRCC wants to see.

As for non-certified records, from what I understand, IRCC does not typically need certified records.
Hope this helps, and good luck to us all!