how can i change or add a specific asset in Asset Bundles package,withou send all old asset where i don't want to change(unity)

Question

I apologize in advance for the bad English because I am a French speaker.

I would like help on a problem regarding the creation and management of DLCs with AssetBundles on unity.

Here's what I would like to do:
I create a game with just one scene (Sceneloader) which is responsible for downloading AssetBundles via a defined list and just loading the scenes, it works as follows:

• At launch it downloads a list (containing the name of the assetBundles, its hash code, its version, and its download link), it then checks if the assetBundles already exists in memory if it is the case it checks the hash version etc... if they are identical it does nothing, if not it downloads a new version and saves on the disk. If the file does not exist it downloads and saves to disk,
• After loading the assetBundles which contains the scenes and the other prefabs and other is instantiated directly to the loading of the scenes which are in the prefabs.

In my list there are currently two assetBundles (one containing the scenes and another containing the prefabs, image, sound etc...)

So what I would like to do:

In the first version of the assetBundles, I would like to send the mainCharacter and two enemies plus some other prefabs in an asset bundles called "MAINASSET", and Two scenes in another asset bundles called "ALLSCENE".

In the second version I would like to send just my mainCharacter (which has been modified) and two scenes (including a new scene and a modified scene2).

All I would like it to be saved on the disk and not just in the cache so that if there is no internet connection we launch the game, or that the items are not downloaded twice. So if there's an internet connection he downloads the list and sees if anything has changed.

If it has changed, it updates the game and saves the update on the disk in this way if there is no internet connection the game can still start being up to date since it is already downloaded the problem is that I don't know how to take to create this second part because I would like the client of the game to have downloaded only the necessary.