Yes, there are even people on HN that have reported successful redemption of tether for USD. You can ask people directly. It's not like this is a rare thing that never happens. If people weren't able to do so you would expect people to actually make claims aginst it.
100% of $0. Tether is entirely a scam by intentional criminals and not a single dollar is in a vault.
They say they're 1:1 backed but have committed obvious financial fraud around this. There's no benefit to them to be even 95% backed, it's 100% or jail, so why would they bother?
This is how they maintain the peg perfectly - it's all fake. They "redeem" their friend's Tether with their personal funds but they won't even try if there's a run.