I'm curious what this entails: 

General purpose code, designing, bases and models, placeholders, and story can be made before the start of the jam.

Is it saying that we can make general purpose code and models before the start of the jam, or is this meant to cover finding pre-existing assets? If we're allowed to use our own general purpose code and placeholders, what's the general rule of thumb on what's too much (for example, designing my levels on graph paper seems perfectly reasonable, but what about blocking out levels in Unity and playing around with the character movement beforehand)?

Thanks!

I'm guessing a good rule of thumb would be that anything you could reuse for another game project is fair game (i.e. Player Movement Scripts,  Non-specific  Environment Models, Blank Slate Sprite Sheets, etc.) as those wouldn't

However, I also would like some more elaboration on that just to make sure everything's a-okay.

What was stated by Rapidfire summarizes it very well. Here are some links to similar questions I answered in previous jams:

https://itch.io/jam/metroidvania-month-6/topic/605675/freebought-assets

https://itch.io/jam/metroidvania-month-7/topic/677025/when-should-we-start-worki...

https://itch.io/jam/metroidvania-month-8/topic/797754/quick-rules-question

https://itch.io/jam/metroidvania-month-8/topic/794612/expanding-upon-a-previous-...

https://itch.io/jam/metroidvania-month-9/topic/916330/pre-made-art-allowed

Can we use some assets from the asset store

Can I make my 2d animations before the jam?

Sounds like we can use pre-made/purchased art assets ( sprites, backgrounds,etc) and any general purpose code you wrote for something else, like level editors?

if i make a notes on how platforms and doors will be located with level numbers, etc... its fine or not? also - does using engines like bitsy, mosi or pocket platformer count?

can you use a web page to make thi

А тема Jema будет известна в начале? 

It's depends on players how to manage 

А пользоваться конструктора и такими как покет код можно? 

Are A.I. created assets or assistance allowed?