https://en.wikipedia.org/wiki/New_England_road_marking_system
1. I've been on the whole general route of Route 2, but very little of US-5 north of White River Jct.
2. Looking at Wikipedia's list makes me think that it's possible that I clinched Route 5. I lived close enough to Palmer, that I could've easily taken MA-67 for a lazy afternoon drive.
3. I thought that I may have clinched Route 17, because I have driven all of the old alignment of CT-2. But I'm not sure I ever took old Route 17 all the way to Egremont, Mass..
I can't think of any of the others that I've ever clinched; unless I clinched 1A. But I'd have to find our where the alignment was in Providence.