Word Usage – Can ‘Miss’ Be Used Instead of ‘Forget’?

They are kind of synonyms but not really interchangeable.

To finish means simply bringing something (a task or activity) to an end, or simply stop doing it:

We finished eating our meal.
_{(In this case you wouldn't use complete: "We completed eating our meal." is not the preferred usage).}

To complete means finish making or doing, such as in:

He completed his Ph.D. in 1983.

But another meaning peculiar to "complete" is making something whole or perfect, or with the meaning of "filling a form"::

• He only needed one thing to complete his happiness.
• Please complete the attached forms.

While to finish means merely bringing something to an end, or stop doing that something, to complete has the acception of fulfilling something.

Lastly, I'll leave you with this I found on the net:

"When you marry the right person, you're complete. When you marry the wrong one, you're finished."

The first thing to say is that you might want to change ‘he’d say he’s curious’ to ‘he’d say he was curious’, because it’s reported speech.

‘And then forget’ is an ellipsed form of ‘And then he would forget . . .’ and there’s nothing grammatically wrong with it (‘then’ can come before or after ‘would’).

In the example

If he had to describe himself in 5 words, he’d say he’s curious. And then forgets to give you 4 more words.

the tenses are out of sequence. For it to work, you’d have to change the verb forms in the first sentence and say

If he has to describe himself in 5 words, he says he’s curious. And then forgets to give you 4 more words.