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You can find it here: Learning Skills (direct link to Drug Making skill)

As well as other information regarding the rest of the game.

It's a bug but not game breaking so there wasn't a hot fix for it. Basically a future quest that wasn't supposed to be active.

Without any information it's hard to help you or give tips but you can try this -> Sakura's quest guide and find where you need help.

The OP had a question about 2 quests. One you can't finish, the other needs Melissa.

I'm not a Dev

There's a guide on the discord

If you mean for Nora, try exploring the basement

Can't.

Melissa.

There is. Her scene is a one time thing. After that you can't replay it unless you made a save point. 

There's a guide for quests on the Discord.

Level up drug making and buy the mortor in one of the shops

During the Save Sakura storyline pick the red fate for Ophelia.

As for the hexanyl you need to level up the skill with gold bars

You can't leave the building until you finish the Save Sakura storyline.

You need to turn it on and off to fill her libido, not fill the 5 eyes.

There's a quest guide on the Discord channel if you need help with anything else.

It's a bug. Can't complete it.

This was fixed in v25.9. It seems you're in v24.8