Is there a rate limit on the API?
For Maps Datasets API, there is a default rate limit of:
3000 queries per minute (QPM) on all read APIs.
600 queries per minute (QPM) on all write write APIs.
Do I have to enable billing?
A valid billing account is required to use the Maps Datasets API, though you won't be charged. See Enable billing to set up your project with a billing account.