USD (United States Dollars).
Yes! You can link your own domain in any of the paid plans.
When you cancel your plan, you will remain on the plan until the end of your billing cycle, at which time the plan will be canceled.
We don't do refunds but you can always try and play around in private. Only subscribe to a plan when you are convinced it is worth it.
We use Stripe to process your payment. It's the same payment provider used in products such as Notion, Shopify, and Slack. We do not handle your credit card information directly.