We guesstimate our dog is now about 5 or 6 years old now, but, we could be way way off, who knows? Buddy won't say how old he is.....The vet said Buddy was too malnourished to make accurate guesses, really, and the vet said, pen in hand---------
"How old do you WANT Buddy to be?" so we said, "only One year old, so we can live with Buddy for a long long time."
and the vet marked down, "One year old he is!"
so now ----------our dog is "about five or six"

but he could be ten, who knows.
I think dogs of any age can learn.
Any age at all.
Even geezer dogs can learn new tricks. (but, one may have to choose less stenuous tricks if the elderly dog has any arthritis or other limitations, but, his mind is still ready to go!)
Some ppl here think some puppies can be more challenging to train than adult dogs, for some things anyway. Some ppl think an adult dog can settle down and focus better, and has more self control,
than some puppies can.
but, DTA has some pretty amazing puppies around here, too!!
i also think any breed of dog, or mutts, can learn tricks, too. Any breed at all.
I THINK ALL DOGS CAN LEARN TRICKS!! Some dogs might need some training-tweaking to find the method that works best for that particular dog,
but, all dogs can learn tricks and cues.