Surfshark is a virtual private network whose own site says many personal plans allow unlimited simultaneous devices, rather than a fixed device cap. It publishes CleanWeb to block ads, trackers, and malware, and Alternative ID on plans that include it, for making a separate contact identity. People use the VPN for private browsing and for streaming.
Apps are offered for common phones, computers, browsers, and some TVs. Surfshark states a money-back guarantee on plans it sells itself. Unlimited devices and Alternative ID are plan details on the Surfshark site, so a shorter plan may not include both.
Where this page shows an Up to cashback rate, that rebate is from KPON, not from Surfshark, and it follows the terms above.