I'm not sure about exceptions for seniors, but if you're a veteran or disabled veteran with credentials you move to the front of the line.
This is what we did. There is an option of same day passes. This opens at 6.30am. But they get filled out pretty quickly. And the second time we did a walk in at 1pm. Limited number of people are allowed to walk in on weekdays at 1pm. Since I was on a holiday these options worked for me.
It's free
I'm not sure, both times I visited the museum it was with a group on a tour bus.
Admission is free for everyone. Just a long wait period. We ordered tickets in March for June admission.
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