Questions:

"While the letter is written sentence by sentence, there are some words (expressions) which are wrong because they have some sort of grammatical mistakes, or an unfavorably different meaning or even tone."

Now as the final paragraph is written, can you just select the most suitable (correct) choice in each sentence?

(red ones are wrong and grey not recommended)

At the moment, to compensate for ↞ | ↠ compensate the delay in completing my assignment, I would very much ↞ | ↠ very like to request a two-week extension on my deadline.

If it is kindly ↞ | ↠ please granted, I, in return, will certainly meet any other extra demand you would like to make ↞ | ↠ give on top of my assigned piece of work.

Once again, I regret ↞ | ↠ regret for any inconvenience caused.

PS. Please find enclosed ↞ | ↠ see attached my incomplete assignment with my compliments.