You can't, since VDB files are baked out sequences that can't be changed afterwards. You can only position them in your scene, scale them and change their materials

Sure! However, you will have a better experience using the addon. It provides preview pictures, timing settings, a search function, automatic materials and automatic unpacking and installing of new VDB files.

The frame rate used for baking is 24fps. You can use the VDB files in animations with higher or lower framerates, but be aware that the timing won't be correct anymore.

This pack only includes VDBs that have nothing to do with fire. Included in this pack are diverse VDBs of smoke, steam, dust, dry ice and some magic effects.

After installing the addon, go into the side panel menu of the 3D viewport (press "N" to open it). Navigate to the "VDB Forge" tab and inside it go to the "Install Packs" tab. After downloading, without unpacking the zip files manually, select the folder in which you downloaded all the zip files by clicking the folder symbol next to the path textbox. If installable zip files were found, you can press "Install VDB Packs". You should see them now in the "Add VDB" tab. If some of the contained VDBs are already installed, the addon will skip them automatically and continue with the ones that are not installed yet.

No, the VDB assets are split up in 5gb folders. You can download them one at a time and don't need all of them to run the addon. Just download the "VDB Forge Addon" zip file and install it in Blender. After that, download as many VDB zip folders as you like. Without unpacking them, install them using the addon.

Blender 4.1 and 4.0:
Edit --> Preferences --> Add-ons --> Install 

Blender 4.2 and above:
Go to Edit --> Preferences --> Add-ons --> Click the small drop down arrow in the top right corner and click "Install from Disk..."

Then locate the downloaded zip folder called "VDB Forge Addon". Double click it and check the checkbox that appears.

After that you need to set up the directory in which the VDB Forge folder structure is set up. All VDB files will be installed in this directory. Make sure hat you have ~116gb of free space in that directory.
Navigate to the location you want the folder structure to be set up in by clicking the folder symbol of the path textbox. After thack, click "Setup Folder Structure in this Directory". 

If you already got a folder structure press "Already Got a Folder Structure" and select it in the path textbox.