Ookkaaaay here come spoilers
The potion for fast hair growth is how you kill the leech queen, you pour it on her and the hairs grow under her and stab her. The "atomizer" (empty perfume bottle") is what you will need to spray the potion on the leech.
The 4 buttons that open valves... just press them all so they all say "unlocked", it's something to do with the "bio-elevator".
You get in through the biogate. On the first screen after the biogate you have to break the horn with the black patches on it. You'll find the fungus spores in it.
Once you've been to the vet's house, read all the papers and opened all the valves by pressing those 4 buttons, you go back out and find all horns that have cracks in them, (there are 4 of them) and say "open horn". The horns will open, and they all have a lever in them. Pull the lever.
Then go to the screen where there's a lone lever that seemingly does nothing. Pull it. A bio-elevator will appear, and you go down in it.
When you go down, as you exit the elevator, in the first scree you need to press a button. You'll get a valve in which you will collect hormones, you'll get the tech cube (you'll need that to get the antidote later, back at the dirtcloud). And you'll get a note which you have to read, which tells you how to find tix eggs.
Then go south, to a chamber where you can milk hormones. You have to pull on the glands hanging from the ceiling. Don't worry if the door shuts, there are three buttons on the wall, you have to push them in some order (give it a few tries) and it will open.
Once you have the hormones you can go back up.
Then go back to where the pool of water is, and you'll find a "tix". Try to catch it and it will run and lead you to its nest. Then you can take its egg. (note that the tix won't appear until have read the note inside the voidbeast!)
When you have all that go back to the house and put it all in the blender and pull its lever. It will automatically put everything into the atomizer.
Then go back and spray the potion on the leech queen. Large hairs will grow and kill her. However as she dies, she will poison the void beast.
You have to go back to the dirt cloud, and put the tech cube (the one you found downstairs inside the void beast) into that gap next to the oval door, and type the combination - first two buttons in the first row, and the last button in the last row. (to be honest, I found this combination in some discussion online, I don't know how you get it in the game, hah)...
It will say the light is now on.
Then go out (east - north) to the "dome interior". Push first the left button then the right. A probe descends and reads your mind. It gives you a formula, made up of some signs. Write them down or take a screen grab.
now go back to the oval door room, and press the long button. It will open a compartment to the south. That's the lab. Enter the formula the probe gave you. It will create the antidote that you need to save the voidbeast. Take it and inject it where the leech queen is.
That's it, you've saved the void beast! Go back to the village, there will be a celebration thank you party for you, and the villagers will give you some valuable items. One of them is the key for that horn with a strange symbol (north off voidbeast's eye).
Go there, put the key in. Another bio-elevator opens. It takes you to the voidbeast's nerve centre, something like that. You have to go there, cos that's where you'll find the letter -K-.
After that, if you like, you can go back to the bar, talk to the phleas some more. One of them will give you a tip to go back to the dirt cloud and use the mind probe again. If you do that, it will give you another combination, and when you type it in it will give you some kinda platinum ball. It's just a "maximum value object" nothing more. So it's up to you if you want it or not.
That should be about it, I've so spoiled the game for you now