Help me with my bucket list so I can learn to mod

All of these are pretty advanced, which one would you want to focus on first?

My post goes backwards, sorry about that.

1. The last one, adding floor animations, is going to be extremely difficult if you want it to work like EA animations. If you're okay with them being subpar and not being able to do anything (aka multitasking and instead just sitting there like a pose), then you can just create your animation and have it work. But if you want everything EA has, it's going to be a mess. For this one to be like EA's, I'd actually recommend waiting for my friend to release his program, as he's making a program for animators so custom animations are easier to create and better (not like the current ones where they float and glitch everywhere because they lack the necessary material). For now I'd recommend just working on adding interactions to stuff and getting use to basic modding, which is the easy part (XML injector by Scumbumbo can inject the the interactions for you, unless you're adamant to learn Python).
   
   
2. Actually, you do want to copy the chess table as it would be the easiest route, at least depending on what you are trying to achieve (we don't have any other board games last I checked). What game are you trying to make? You'll need to extract everything chess related and make alterations that way.
   
   
3. The XML you just eventually learn after poking at it for a while. There are tutorials that ease this process but they don't cover everything. Follow this tutorial series on getting started and for tutorials on different types of tuning mods (note that I said series, I linked page 2 as that is where you start to learn programs and setup):
   simsvip.com/category/the-sims-4/how-to-create-a-mod/page/2/
   
   And these ones teach you how to use the TDESC and some other basics.
   www.patreon.com/posts/tutorial-very-30543199
   www.patreon.com/posts/bonus-tutorial-31960337
   www.patreon.com/posts/bonus-tutorial-31988039
   www.patreon.com/posts/bonus-tutorial-2-32028544
   TDESC browser: www.modthesims.info/download.php?&t=618199
   
   The same person also has a ton of other tutorials, like creating loots, buffs, interactions, etc. so here is the main tutorial page www.patreon.com/zer0_/posts?tag=Tutorials
   Once you have your modding folder setup and read the basic tutorials, try looking through the slob files. It might be in the trait itself, or the flush toilet interaction, or something similar. 
   
   
4. The door sound is easy enough, it should be in the animation (if not there, it would be referenced in the XML, which is rare). Sigma posted a mini-tutorial on how to locate sounds in animations here: sims4studio.com/post/135615/thread
   
   Once you've located the door sound then you can copy the sound name, convert it to FNV64, open Game Cruiser again and paste it. This should lead you to the audio file. You have to go through all this work because audio files are not named and can't be searched by name like most other files.
   
   
5. The dirty textures I'm not sure as I didn't see them in debug or CAS, so most likely you'd be able to find them in Game Cruiser as something else (Sigma shows you how to access Game Cruiser in the above tutorial). Game Cruiser is how you find anything not in CAS, Build/Buy, or XML, in a semi-organized way. There is no tutorial as far as I know on how to use it, before you ask. xD Let's just hope the hygiene texture isn't actually a VFX, otherwise there is no replacing it, only turning it off.
   

I got curious so went digging (Google to the rescue) and found this tutorial explaining where burn and dirty states are for objects (I thought they were a geostate, weird way to do this): sims4studio.com/thread/5183/tutorial-change-dirty-state-overlay
There is also this tutorial by Peacemaker. peacemaker-ic.tumblr.com/post/148590251499/dirtytexturetutorialpartone
I'll keep looking for sims though.

Sorry, I gave you a starting point with the sound as I thought you were going to go from there with research (and also because of how you would go about replacing it). xD You can either replace the sound in the audio file you located, or make a new sound file and replace the reference in all animations. Replacing the sound in the current audio file is the easiest. Unless it's used for something else, which I doubt, I don't think it will be a problem. Here is Necrodog's tutorial, which isn't really the best for explaining replacement, but is good for new ones. 
If you want to create a new sound file, you can also use the sound tool (which explains audio settings you'll need too), which is on an adult website so I can't link it (meaning you need to be 18+, or whatever the age in your country). Search "sims 4 sound tool" and it should come up. 

It's not too difficult to make custom objects when you clone and use most, if not all, resources from the game (entirely new custom ones with custom animations, etc. are much more involved, and of course, way harder if you want them to look good), it's just a lot of moving pieces you have to change and alter as that is how the game is built. Someone very recently, as a complete beginner, did what you wanted to do and made a "new" board game with the Deaderpool/MCCC Discord server's help. As for the animation tool, I don't know when he will get it done. You may be waiting several months or longer to use it. If you are new to animating I'd recommend learning and practicing in the meantime so that when it releases you can just import and export as needed.

MizoreYukii hercy

I actually managed to find the grubby texture trough some convoluted methods

grubby texture: 00B2D882!00000000!83D7255E72389859

you can add it to a package by going to the game file cruiser



then just copy the instance id where it says "instance", check the DST texture checkbox, select the entry that appeared, and click on add to the package



I did a quick test by changing the hue/saturation in photoshop to see if it actually works, and it works fine :)

oh its a little convoluted, i used ninja ripper to rip the texture from memory, since ninja ripper only extracts the textures that are currently loaded there won't be that many files (i had 264) after that i skimmed trough them and found the grubby texture, now to find the instance id i extracted all the "DST image" from the "game file cruiser", sims 4 studio will name each texture with its: instance, group and type.

then i copied the texture that i extracted with ninja ripper to that folder and used a software that finds duplicate images, and i got it

No, if you clone an expansion pack hairstyle, it won't work if that other person doesn't have that pack