Hello all! I'm new to home bike maintenance/upgrading and looking for a little helpful advice with some questions.

I have a Giant Quasar (circa 1989-1990) that I use as a commuting bike (picked it up off Craigslist a few years ago). It's got a Suntour Accushift drivetrain (52/42 crankrings, 13-26 6 speed freewheel, rear derailleur says "Suntour VX Accushift" on the body and "Accushift Plus" on the arm). Based on the component date coding from the Vintage Trek website, I think the rear derailleur was made in 1989, so it's possibly original to the bike. I'm looking to give myself some lower gear options and had two questions.

(1) I'm considering swapping the inner chainring (42 tooth) for something smaller, maybe a 38 or 39-tooth. But the chainring bolts are smooth/rounded on the inside - i.e., they don't have the hexagonal shape one would expect to fit an allen wrench. And it doesn't look like they've been over-torqued or rounded off, because all of the bolts look the same. It looks more like they were pressed or riveted in and never intended to be removed. Has anyone seen anything like this? Took it to my LBS, where they said they'd only seen that on cheap, low-end 'big box store' type bikes. Any ideas for removing this type of chainring bolt?

(2) If I can't change out the chainring (or possibly even if I can), I'm planning to swap the current 13-26 freewheel for a 13-32 freewheel. I can't find much information about whether the Accushift/Accushift Plus rear derailleur will handle a large cog/freewheel that large. Will I need to swap it out for a long-cage derailleur? If so, does anyone have recommendations for a good compatible long-cage model?

Thanks!