1: I don't use this for online play, basically ever, but I've never heard of anyone getting in trouble for this. I think this is largely because of the game's built-in function of making sure player's have matching files, so you'd never be considered cheating. I can't say with 100% certainty, though. However, for offline play (you don't need to disconnect or anything, just play against the computer), you'll definitely be fine.
2: Ignore the multiplayer section. It needs rewritten. Just download the core and art and the DLL (it's in the folder with the core and goes in your game directory like everything else). The multiplayer utility doesn't work. If you want to make it automatically update (it's still updated every day), then add the Core (and optionally the art) folder to your google drive so they're downloaded automatically, and then download the sync tool. Run the sync tool, tell it what it asks. Put a shortcut to the sync tool in your startup folder. You're done.
3: Any deck can be used in online play so long as both players have the deck. But in general, yes, those decks will be easier. Getting all of the decks would be... a lot, but you're welcome to it. If you're going to play multiplayer, though, you'd be better off getting some number of
sets of decks and letting a specific person know which sets to get. This is because the sync tool can handle sets of decks if you've added the decks folder to google drive so it downloads and make sure you've set the path in the ini if you didn't do this when you first ran it (and if you don't want to mess with the ini, then delete the ini and run the tool again). The ini needs the following line: "DecksFolder=C:\Google Drive\Community Wad Folders\Community Wad Decks" where you replace the path with the correct one. Once this is done, right click the tool (in your notification area by your clock) and choose Register CPE ID (CPE=Content Pack Enabler). Type the number of the set you want to try. You can register as many as you want. My decks use the CPE ID 9009, TFM uses TFM (the only non-number), Kithkin uses 1314 (I don't know who made the others, so just try them out and see, or search the forums for the number to see what you come up with, you might find the deck list). Once they're registered, right click it again and click Sync Decks. The sync utility will keep the core and art files up to date automatically, but it will never automatically sync decks. You'll need to tell it when you want to. This way, you can tell whoever you're going to play against that you're using cpe ids:
X, Y, and Z, let them register those, register the ones they're using, and load up the game.
Content Pack Enabler is a small file that tells the game a given deck should be available. Without it, the decks don't show up in game. Each deck has a number (except TFM's), and the first few characters in that number are the same for all decks made by the same person. That person's CPE (because each person has his or her own) has that number as well. As an example, I use 9009. So, my CPE is named "Data_DLC_9009_Content_Pack_Enabler.wad" and my decks have 9009001, 9009002, 9009003, and so on.
If you want to skip the above and just download everything, that's perfectly doable. In the decks folder, there's a 7z file named "CW Decks.7z". Download that and extract it (using 7-zip or anything else that can extract it) to your game folder. It always contains all decks and content pack enablers.
As a quick rundown, from the beginning, of everything you
need to have all decks work:
- CW Core
- CW Art files (core and update)
- d3dx9_43.dll (in the folder with the core)
- CW Decks.7z
If you want basic lands to have the ability to manually be tapped for mana, you'll need RiiakShiNal's Manual Mana Mod (there's a link in the CW OP). Everything either goes in or is extracted to your game folder.
I'm sorry if this is confusing. Feel free to ask any questions you have.