So lets say i adopt my step dayghter and complete the adoption paper and then i sponsor both of them i just need to use spousal sponsorship and include adoption paper.Perfectly straightforward and no particular issues. Probably the easiest and most straightforward for now. Obviously you'll have to deal with the provincial adoption process in Canada but no urgency.
You're overthinking. You do not need it. This is for cases when adopting children outside of the immediate family. It is not relevant to your case - particularly since you have not adopted yet.
You are not sponsoring your adopted child, you are sponsoring your spouse + dependents.
If adoption is going to take longer then i can start the adoption process and use same Spousal Sponsorship application and inform IRCC in a small letter that the adoption is in process and update IRCC with adoption paper when it is done.
The adopted children application does not apply to me in any scenario whether the adoption is done or it is in process.
If i decide to adopt her in Canada then it is a completely different process.