Do auxillary verbs like will, can, shall and the like have past participles? I f so, how are they formed?

Answer 1

Try "would have," "could have," and "should have."

I will go.
I would have gone.

You can also you "would" and "could" alone in certain circumstances.

"When I was young, I would go to the store every Saturday for comic books."

"When I was young, you could buy a comic book for a dime."

There is no equivalent for should.