The company doesn't have to answer every question but it would be a huge red flag if the company could not answer any of them.
Getting this information is done in the form of an application
Good senior people are selective and want to know a lot about the companies they might be joining. If they didn't ask perceptive questions I'd think it was a red flag.
I mean seriously, a startup is trying to hire a senior engineer, is offering less base salary than Google, stock with an average value of nothing and they don't even want to answer the hard questions? How would they ever hire anyone good?
The only people I'd give a pass on not knowing asking good questions in an interview are interns or new grads.