Do you think the versions with and without the definite article are interchangeable in the sentences below?
My Answer is no they are not interchangeable and the sentences all sound incorrect in any variation.
- I play multiplayer of Modern Warfare. or 1a. I play the multiplayer of Modern Warfare.
Both sentences sound awkward, play and multiplayer is basically repeating yourself with consecutive words. Modern warfare is not specific, unless you have already highlighted the topic. Therefore we should state that it is a game and we are going to name it so we write "The game blah blah" So yes we may use the definite article albeit in a different way to which you have tried to use it (see my answer to items 3 & 4). Finally you have made a definite statement you always use multiplayer mode, never ever single-player. Although this could be true I would use a less definite tone.
I use the multiplayer mode of the game Modern Warfare,
alternatively (presuming the reader knows Modern Warfare is a game), what I think sounds better in spoken English is;
I prefer multiplayer mode when playing Modern Warfare
- I play singleplayer of Modern Warfare or 2a. I play the singleplayer of Modern Warfare
again as in Item 1
I prefer single-player mode when playing Modern Warfare
- Do you play multiplayer/the multiplayer in Modern Warfare?
4.Do you play single-player/the single-player in Modern Warfare?
I would replace with
When playing the game Modern Warfare, which mode do you use, Single or Multiplayer?
The definite article We use the definite article in front of a noun when we believe the listener/reader knows exactly what we are referring to: So here we have used the noun Game and the name of the game so no one is doubt of what we are talking about.
In your examples you had tried to use the definite article with the "adjective multiplayer". which is incorrect. The definite article: 'the'
multiplayer; adjective; used to refer to computer games in which several players can compete against each other:
Ref; CED multiplayer
game; noun; game noun (FUN ACTIVITY/SPORT) an entertaining activity or sport
Ref; CED Game