I live just out side the San Francisco Bay Area, in a relatively small town with the beauty of the sun and warmth during the summer surrounded by trees and foliage. In my backyard is a swimming pool and patio area where my Miniature Schnauzers and I get together on a daily basis. It is so heart warming to watch then play with each other them to come to me to give and receive love and assurance.
I truly believe that many but not all dogs can be trained to do several different tasks, for example, I am a Miniature Schnauzer Breeder and one puppy owner trained her dog to be a Miniature Schnauzer diabetic service dog. For me that certainly was a first. She trained her girl Ruby in both obedience and agility.
The top 2 tiers of dogs listed in dog obedience intelligence rating can certainly be trained for many different types of obedience, service or more.