If you purchase a day pass that is good for 7 days can you use that and pay the difference for an annual pass?

Not anymore it used to be that way

No

I have a seniors pass. I can go through any national park free. Love it.

Unfortunately no! 😏😏😏

I guess not, but if that doesn't mean that there is no pass that will work like that, so you may want to make a direct inquiry with the people who run the place directly.

Nope