Yes. Both DLCs are implemented in this mod and have seperate description packages.

Yes. you can get those here:
https://moddingofisaac.com/mod/1079/external-item-descriptions

Mods don't disable achievements, as long as you have killed moms Foot (Endboss of stage 6) at least once on the savefile. Kills on challenges or dailys dont count.

Quoted from the wiki:
" Playing with any enabled mod prevents any achievements from being unlocked.
If you have beat Mom at least once, achievements will no longer be locked."

Simply press the "subscribe" button on the Workshop page. This will automatically download and install the mod. Just start your game again afterwards, and the mod will be listed in the "mods" menu in the main menu where it can be activated/deactivated.

You need to have all DLCs of this game installed! Workshop mods only work with Afterbirth+

1. Try pressing F2 ingame to unhide the descriptions.
   
2. Check if the mod is listed and enabled in the "mods" menu. See the question below if that is not the case.
   
3. Disable all other mods you have installed and see if one of those caused any errors.
   
4. Check if your run currently is affected by "Curse of the Blind". On default, descriptions arent displayed when the curse is active.
   
5. Check if the debug Console displays any error message (How to open the debug console[bindingofisaacrebirth.gamepedia.com])
   
6. Execute the "Verify Game cache files" function in steam for the Game. Step by step guide can be found here Verify Game Cache Files [inxile.zendesk.com]
   
7. Cleanly reinstall the mod: See FAQ entry "How to cleanly reinstall the mod"

Steam normally automatically updates all the workshop mods you have installed. sometimes though, this automatic process can fail, or wasnt completed correctly. For that purpose, a clean reinstallation of the mod might help fix some issues:

1. Unsubscribe from the mod.
   
2. start the game and go into the main menu (this will uninstall the mod properly)
   
3. close game
   
4. subscribe to the mod (this installs the mod again)
   
5. start the game and enter the main menu

if the mod is not visible in the mods folder even after you subscribed to the mod, it could be caused by the following:

1. You dont own all DLCs (Afterbirth and Afterbirth+). All Steam Workshop mods require those two DLCs to be installed in order for them to work correctly.
   
   
2. Your Windows / Mac Username does contain special characters, that are not part of the standard english alphabet. Since the game is not able to interpret those correctly, it cant find the mods folder. In order to fix this issue, you sadly have to create a new Windows User on your computer which name only contains english characters.

The simplest way to edit the config is to use the mod "Mod Config Menu".

Alternatively, you can change the config manually following these steps.
Windows
1. With Repentance: steamapps\common\The Binding of Isaac Rebirth\mods\external item descriptions_836319872\
1. With AB+: ..\Documents\My Games\Binding of Isaac Afterbirth+ Mods\External item descriptions\
2. Open "eid_config.lua" with any texteditor
3. Edit the Config file
4. Save the file
5. Play the game

To reset the config to default delete all the "save[NUMBER].dat" files from the following folder:
1. With Repentance: steamapps\common\The Binding of Isaac Rebirth\data\external item descriptions\
1. With AB+: ..\Documents\My Games\Binding of Isaac Afterbirth+ Mods\External item descriptions\

Linux / Ubuntu
Same as aboth but the path is: /home/%YourUsernameHere%/.steam/steam/steamapps/workshop/content/250900/836319872

Simply install "Mod Config Menu", open it and navigate into EID -> General -> Language


--luadebug is a launch option of the game that allows mods to use all features of the system, granting it full file system access, internet access and other potentially harmful features.
In EID, it is used to access the log.txt file of the game in order to read effects of TMTRAINER items.
Because --luadebug can be abused for malicious intends, we highly advise you to only enable it if you know what you are doing and trust all the mods you have installed!
How to enable --luadebug:
1. Open Steam.
2. Click on the "Library" tab near the top of the screen.
3. Right-click on "The Binding of Isaac: Rebirth" and select "Properties".
4. Click on the "General" tab on the left.
5. At the bottom of the screen, there will be a box to specify "Launch Options".
6. write the following into the box: --luadebug
7. start the game