1) Payment is done using Paypal-service. If you don't have a Paypal account you can make on at www.paypal.com using most of the regular credit cards. Paypal account is required in order to start using the service. See Paypal.com for more details.
2) When you buy a digital procuct, it is available for you for 30 days until it expires.
3) Provider is not responsible for any country specific technical, political or equivalent restraint that may prevent you using the Service in your country. Inspirationalmath.com uses Vimeo as the main video server. Make sure vimeo.com is not blocked in your country before buying.