Hi, we have production and sandbox environment. Our production is in version 2020.2 but sandbox is in version 2020.1. Should sandbox be upgraded automatically or should we always refresh sandbox if we want to get new version?

You (well, administrators) should have had an email from NetSuite telling you when the sandbox upgrades are. We were upgraded last weekend and our sandbox upgrades were pushed back to this weekend & early next week. You may well be in the same situation