I am trying to copy information (objects and type) from an already completed project to a side project where everything needs to be identical to its original. When I am copying my grouped selection from my CC document and pasting it into the new one the objects become subject to what appears to be a default stroke and fill rather than retaining the original attributes from the existing file.
Could you please advise me on how to amend this issue.
This is most probably because you might have altered the default object style (name like "Default object style") and not created a new one. Once you copy the objects to the other document, where it also has a default object style with that name, that object style is not overwritten (exactly because the name is equal) and the properties of that other style are applied.
Solution: never use default objects styles. This is sometimes wanted to have paragraph or object styles with same names in different document, which only differ, for example, in the language setting.