"What is happened" is wrong. You can say either "What has happened to this world?" to ask about recent events and their effect on the world today (present perfect) or "What is happening to this world?" to ask about events that are happening at the moment (present continuous). Please don't take English lessons from this friend of yours!

What has happened in in the present perfect tense, and what is happening is progressive/ continuous. What has happened refers to a past problem/situation, but there is still a connection to the present, what is going on right at the moment of the question. What is happening? Is asking about all that is going to at the current time, the right now, so to speak. I do not know if that helps you or not. Please contact me if you have questions or if you want to use the two is sentences and send them to me, I can check your sentences for you. Have a wonderful day!!! :)

Sorry, no. 'What is happened' is wrong, and there is no such thing as a 'relative present past'.

HI what is happened is in a relative present past and it is more of an expression ! what is happening? is a question and it is referring to something that is going on right now in the present.