1. Output: Reference error. As age not found.

2.

• map() is used when we want to output in terms array. return is used.
• forEach() is used when we want output line by line. console.log() is used.

3.

• 

This will give UndefinedOutput. As the return is used in a forEach callback function.

• The correct way of writing the above code is

Console.log is used instead of return.

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If inside callback function argument is not passed. It will give REFERENCE ERROR as value not found.

4.

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Run Time Error if matrix[]3x3 is there and we do console.log(arr[2][4]). It will give Exception error Out of bound spaces as this memory is not allocated.