Tutor:Is this mean if learner submit answer this extension help to show feedback on that question?

Yes, it shows the feedback in a popup.

Assessment: To create assessment in Adapt?

Yes

Assessment Results:To show pass/fail ?

Yes. This also has the 'retry assessment' functionality. You can actually see that in the screenshot here.

Trickle

I'm not sure I can give you a better explanation than the one in the README. maybe also look at the demo animated gif in there?

and Background

I don't know what this is.

Have you looked at the demo course here? Most of what you are asking about is in there.

I will be working on building course with assessment and I believe I need  to use all above mentioned extension?

You don't need to use Trickle but most people like to use it to make Adapt show the assessment questions one at a time so that the learner can't miss one.