As the OP is new to this site, I think she is quite right to err on the side of caution. It is not often that newcomers get genuine invitations within a short time of joining.
The wording of the job offer, was slightly off. I have never had a client (or any employer in the B & M world for that matter) tell me in an invitation to interview how old he is, for example.
I don't spend too much time trying to evaluate the situation if it is in a "gray" area... might be a scam might not be. If the client or offer seems a little weird, I'll still accept an invitation and agree to do work if the work is the kind of work I regularly do and the client agrees to my rate.
If I accept an actual, official Upwork job offer and log hourly time properly, there's not much that can go wrong for me.
Example: Last month I worked for a client in India for a couple of weeks. First week was fine. During second week Upwork suspended the contract, saying there was a problem with the client's payment method. The client told me this was due to Indian demonetization, which is a real thing.
I don't know if the client was 100% honest or not. Upwork ended up having trouble billing the client. But here's the thing: I STILL GOT PAID. Upwork came through with their payment guarantee and I was paid for all the time I worked on the project.
So... If I know a client is a scammer, I waste no time talking to them. Scammers don't contact me, though, so this is rarely an issue for me.
If I'm not sure a client is a scammer, I treat them the same way I treat all clients:
If they hire me, I'll work for them. If they don't hire me, I don't work for them.
You don't get paid by somebody who doesn't officially hire you, whether they're a scammer or not. So it's a waste of my time to give it too much thought or "research."
I see the interviews you are referring to and I'll forward them to our Marketplace Quality team for a review. If they found that the clients are violating Upwork ToS, they'll take actions against those jobs.