>Did you read the SRE handbook before applying?

Yes, but it wasn't really necessary. Google isn't trying to hire SREs, they're trying to hire SWEs and specialists who they can turn into SREs, if that makes sense. Though I'm sure SRE experience elsewhere helps, they are still expecting SWE level coding/algorithms etc.

>How do you decide who gets alerts

SREs will be assigned to a team that has a rapidly growing service or essential service (or both), and they will be the primary team that takes the alerts, while the developers have a slower SLO (though still oncall rotations for them).