Grammar and vocabulary

Hello, I have questions in the following sentences. If you answer my questions, I thank you for answering.

Q1. Which one of three is correct?

How many do you think countless other people have the same scenario?

How many countless do you think other people have the same scenario?

How many countless other people do you think have the same scenario?

Q2, The few times that aggressive conflicts occur, it is the possessor that tries to make someone leave the circle.

Is it grammatically correct to write as below instead of the sentence above?

The few times when aggressive conflicts occur,

The few times aggressive conflicts occur,

Q3. Is it the same meaning if I use the word ‘cited’ instead of the word ‘named’?

Surveys conducted during those times asked citizens to choose two “especially important” events from the past seventy years. Two weeks prior to the anniversary, before the media blitz began, about 30 percent of respondents named 9/11.

Q4. ? Is it the same meaning if I use the word ‘harnessed’ instead of the word ‘used’?

? Does it mean the same thing if I change ‘through the burning of coal’ to ‘through burning coal’ ?

In a single week, the sun delivers more energy to our planet than humanity has used through the burning of coal, oil, and natural gas through all of human history.

Q5. Is it the same meaning if I use the word ‘employ’ instead of the word ‘use’?

Our challenge, and our opportunity, is to learn to efficiently and cheaply use the much more abundant source that is the new energy striking our planet each day from the sun.

Please reply.