When Changing Code's Written by Some One Else!!!!

What will be your primary aim, what should you look for when you have asked for changing an existing code written by some one else?

Is that what something related to coding conventions like
Variable name and their uses
Descriptive class names
Number of comments through out the code

You will get a clear idea if you consider this situation,
Suppose you are asking a real estate broker about a house, his first statement should not be about the color & quality of the paint, because that may not be a reason to make you a prospective buyer. You can easily repaint your house you can easily have someone else repaint your house, but you cannot easily change its foundation.

Like this your 1st priority needs to be slow-performing algorithms or insecure code. Coding. Conventions are useful and important! But since the formatting of code can be change easily.

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