Please find my responses below:
1. Once the request limit is reached the map will stop displaying, and a message will be displayed within the map container stating that something went wrong. That being said the odd’s of reaching 25000 requests a day are quite slim as requests as highly optimized in WP Google Maps.
2. In your example of 100 markers being loaded on the map page, only a single request is made. This is because we only request the map once, and then place markers on the map.
A request is measured by the amount of time the page is viewed in a day.