Limits to telescope size

Just seen some pictures of Hubble, and The "Very Large Telescope"
(original name) in Chile. It made me think.

With a reasonable space based industry, moon mining, metal working,
aluminium and glass production, precision engineering, how big an
optical telescope could be built in zero-g?

What are the limits? Could a 100m diameter optical telescope be built?
what would it see?

As for radio telescopes, what are the limits are baseline inferometry?
what would a few telescopes, each say 3km across, in solar orbit, say 1
billion km apart be able to achieve?