I want to register for the SAT, paper registration is currently not available in my country(Ethiopia), and I want to register online. Credit card and any other form of online payment is not possible in our country, but i have a close relative in the US. Is there any way he can pay for me without him giving me his credit card number and any other personal info(he can't fill out the form for me because the questions on the form are personal and can only be answered by me) and he is not a tech savvy guy so he can't do anything complicated, so is there a simple way to do this that doesn't take much time?
Your relative in the US could buy a pre-paid Visa (aka Visa gift card) and give you the numbers on that to pay. They're available for purchase at many grocery/convenience stores. In most (all??) cases there'll be a fee of a several dollars charged in addition to the face value of the card.
The biggest headache I can think of would be that pre-paid cards are generally only available in $25/50/100 increments; unless the current SAT price matches one of the standard increments they'll have to buy the next card size up and then get the remaining money off it in a separate transaction. A grocery store would be one of the easier places for your relative to do this because cashiers there are used to splitting transactions across multiple payment sources (something not true at most other types of business) due to regularly processing transactions partially paid for via welfare benefits.