Questions to ask to the Hiring Manager during Interview?

I have a final interview coming up, with a "seemingly" cool and successful IoT Startup. I would like to make sure that the role (Backend/Data Engineer), at this org, is really what I am looking for. I don't want them to trick me, telling me BS how cool/impactful what they are doing is, and then later after joining, finding out that the role/product/project has minor impact and does not support my career growth.

I am searching for a role/product combination that will challenge me technically. Where I can grow technically and I can be proud of my achievements for my following career steps. I have often applied to companies that simply lie big during the interviews about how awesome the position is, and how impactful it is....but when joining I end working on products or projects that either never make it to production or never reach past a couple of users (less than 500). Although those products were technically built up to the business requirements (i.e. failure was not due to weak implementation, but rather bad market fit or business/marketing or solving of a non-existent problem).

How do you earn sure that company/role/product you apply for, are really what you expect and what is your strategy to avoid bullshit?

• Read online regarding them (not on their website or their marketing material which is extremely biased toward BS)
• Have good questions during the interview but make certain they dont start to hate you (which questions are those)
• Ask to spend a day on the office? I did this once and I rejected the company since I saw a huge discrepancy between the verbal interview and the real operations

What else do you recommend?