CharlesWantsIn said:
Can a Canadian Citizen adopt a British citizen who in an adult?
UK adults cannot be adopted. (https://www.gov.uk/child-adoption/overview)
Code:
To be adopted, a child must:
be under the age of 18 when the adoption application is made
not be (or have never been) married or in a civil partnership
Some advice from a fellow Brit.
Having read your other posts, I understand that you are desperate but this really is scraping the bottom of the barrel.
Your best, and probably only solution, given your educational qualifications is to find a nice Canadian and marry them. However, proving that it's not a "marriage of convenience" will take some doing. Good luck... I think you are going to need it.
What I would say is, don't do anything that will get you expelled from Canada and barred from returning. Where there is a will, there is often a way, but shooting yourself in the foot early on is not a good idea.