Clicking noise when cranks rotate
That sounds like the bottom bracket bearings to me.

It could be the chain, but you can eliminate that by loosening the rear wheel and slipping the chain off the chainring.

It's not chainring bolts as these only creak under load. It's not the bottom bracket cups for the same reason.

You appear to have a loose ball bearing bottom bracket with an axle with square tapers that the cranks fit onto. I linked a video below that shows how to service this type of bearings. When you say 'Both bolts on each side are stripped' I think you mean the end-caps. You should be able to get those off by jamming something that will engage with the rounded off hex hole. I'd try a large screwdriver with a tapered head.