First is simple past and second one is Past perfect

Avidlearnersecond one is Past perfect

The second is present perfect; past perfect would be I had completed.

OOPS, it was a blunder. in near future i will be more attentive. i am greatly thankful to you.

Then what is the different between,
"He has completed." and "He had completed."

I have completed
It shows present perfect means an activity has finished in near past
For example
I have completed my work so I can play now. (Today)
I had completed
It shows past perfect
For example
I had completed my work, I could play after that. (yesterday)

Thank you for your support Avidlearner..

In the above fivejedjon has told to someone that "would be/had completed" are past perfect..
Then "could be completed" is also a past perfect??

Dilshi, he said that past perfect would be "had "completed".

in other way, past perfect is "had completed"

he did not not use inverted commas. why are you using?

Oh yep.. I saw that "I" as a "/"..
Thanks friend..

AvidlearnerhHe did not not use inverted commas. wWhy are you using them?

I used italics. Dilshi use inverted commas. Both are fine.