Do service dogs need to be certified?

Certifying your service animal is 100% unnecessary. ada.gov will tell you everything you need to know about service animals. google it and find a place near you that will "test" your dog, charge you a bunch of money and then give you a piece of paper that you bear NO legal obligation to have.
There is no real Service Dog registration. To have a Service Dog you must be disabled and the dog must have trained tasks to mitigate that disability. IE Comforting someone is not a task, but a trained alert to medical conditions is. Faking a Service Dog can be up to a year in jail.