@LoriBeard I believe it was released Sept 4th, as per the blog article I linked:
https://www.netlify.com/blog/new-pricing-credits/
It also mentions that same date in the billing documentation here:
https://docs.netlify.com/manage/accounts-and-billing/billing/overview/
Credit-based plans for new accounts
Starting on September 4, 2025, all new Netlify accounts will use the new credit-based pricing plans.
To answer your other questions, you should just read the billing documentation.
The documentation for the Legacy Plan billing is here:
https://docs.netlify.com/manage/accounts-and-billing/billing/billing-for-legacy-plans/billing-for-legacy-plans/
https://docs.netlify.com/manage/accounts-and-billing/billing/billing-for-legacy-plans/legacy-pricing-plans/
To put the builds/deployments in perspective though.
Prior to this change, production deploys weren’t directly metered, and the free plan had a ‘build minutes’ limit of “300 minutes/month”, so mileage would vary based on how efficient your build was.
With the new credit based pricing, build efficiency doesn’t matter, but ‘300 credits’ only allows for ‘20 production deploys’ per month (and no other resources).