Authorize.Net is a payment gateway service provider allowing merchants to accept credit card and electronic check payments through their Web site and over an IP (Internet Protocol) connection. It claims to have a large user base of over 400,000 merchants. Authorize.Net integrates perfectly with typical ecommerce softwares and can be used for any internally coded storefront you have. It lets you manage and review transactions, configure account settings, view account statements, download reports, and more through a password-protected website - the Merchant Interface. Its support features include 24/7 support, Blog, Email, FAQ, Help Desk, Knowledge base, Live chat and Phone Support.
Yes, the PayPals Rest API can be used by Merchant in 202 countries. It covers most of the countries and to be sure you may look up for your country here: https://www.paypal.com/us/webapps/mpp/country-worldwidePayment Gateways (US) PayPal