HLR next week

Spent alot of time in this forum last year and finally submitted a claim for MDD secondary to tinnitus. I had all my ducks in a row, or so I thought. I had my therapist's diagnosis and nexus letter, a seperate 3rd party nexus letter, and 2 buddy letters. Submitted June 2nd, denied Sept 19th.

Since the claim denial, I filed for an HLR, heard back from the VA today and have my informal review next week.

My questions are:

-what are these HLR's like?

-Is it like a C&P exam again?

-What information should I have on hand with me?

-If the claim is found in your favor, is there another wait for the actual rating or do they tell you then and there?

Sorry for the dumb questions, everything I was looking at or studying last year was about the claim, but, never what would happen if the claim was denied. Thanks for any help pointing in the right direction