In principle, yes, but as things stand you'll be starting 5 separate TLS connections to the server that way. My feeling is that this would be an unusual way to use serverless functions. Is it something you think you'd do?
Yes. You only have to open these connections once on the first execution of that function (cold start), any future request that hit this warm function will have 5 open connections and can instantly execute these queries in parallel. No overhead at all to open the connections.
What would be the alternative? Only execute the queries in sequence, one by one?
What would be the alternative? Only execute the queries in sequence, one by one?