I consider people knows how to play akali, this is NOT a beginner guide if you try to figure out how to play akali it's not here.
Akali hullbreaker is not a must but more an option, she has many counters
True Damage / Shield / HP max dealer in enemy team / Champion that can sustain on you (aatrox, fiora) / Champion that can long fight you (Aatrox, Darius, Fiora)
Akali hullbreaker is decent against squishies + when enemy team can't manage your split
Important : Some games are really not up for akali hullbreaker, you need to dps as much as you can but if they can lock CC, also if you're solo ap don't play this build. You need to make sure that your team composition have enough damage.

Why Grasp?
Better trade early
Good scaling with Sunderer
Conqueror is not useful against tanks

Why Conq?
The problem with grasp, it lacks of damage when you don't have 3 items when conqueror can snowball because it's akali, damage stays pretty much the same but on a different distribution
It makes akali early way more better / mid game
Legend Alacrity when they don't have CC cause it's more enjoyable
Conditioning is really in the best scenario, your goal is still to survive the laning phase and not ending in 0/5
Bone Plating / Second Wind
Also for the question of presence of mind, it's useful only when you are up to multi kill with akali cause it increases a little bit your DPS, otherwise Triumph.

Rush Sunderer is also fine, but hullbreaker gives you pickaxe which is important for level 6 all in then you can kinda snowball your lane. The item also brings you resistance and a good HP poool

Don't ever finish Bramble item it's useless, keep it and sell it in late game because normally your team will do some but for an early it's still important.
Nature Force is really good against 2-3 AP
If the enemy comp is balanced in term of damage (50% AP/ 50AD%) you better go death dance and embrace demoniac

Split push is the biggest part of this build, I won't learn how to split there because there are many videos about it.
Don't abandon your farm, it's really important to have a good CS'ing and XP Lead.

it's in general Akali top so there are other guides that can help you about this.

I am currently Master Akali top main, but I am still trying limit test with this build. Currently I don't have a really good winrate because I am still not sure if it works in Master + but all I can say at the moment is that the build works to D2 at least, I will update this chapter if I find a way to make it succesful in master. So I don't recommand this build in master+ yet,it's kinda for me to be honest and keep a trace of it