Grammar Differences – ‘What Color Is Your Car?’ vs ‘What Is the Color of Your Car?’

After and Next are not interchangeable.

Your examples:

1. "After Monday, I'm going back to school."
2. "Next Monday, I'm going back to school."

"After" in this sentence implies that you are not going to school Monday, but you will later. Using "next" here means you're going to go to school when Monday occurs.

1. "I'm going back to school after"
2. "I'm going back to school next"

The first example here is grammatically wrong. It's not a complete sentence. "After" is a preposition, and prepositions need to be followed by a noun, unless it's implied. The response to "I'm going back to school after" would be "After what?".

Next would be correct here. This sentence is implying the next action to be completed is going back to school.

It's either deliberately "wrong" English as slang (for humorous effect) or dialect. There are some English dialects that don't conjugate the verb in a "standard" way, but these are usually spoken not written.

Alternately these might simply be misspellings or laziness. Most of the questions in your search use the construction "what means X?" which is a kind of slang-y inversion of the expression:

X means what?

Note this also is not "formal" English, but I don't think it's considered wrong. The expression "what means X?" is a kind of "baby-talk", though, used to indicate a low level of development or intelligence (like "give cookie!" or "Mommy slow!"), so someone might think it sounds funny to speak that way.

Curious that it shows up on the Japanese language SE though. It could be these are not native English speakers who are also learning Japanese.

My guess is that, if it is slang, it's a passing fad and not something you would emulate. For example, there is a "I can haz cheeseburger?" website that, some years ago, really started the whole "lolcat" and "lolspeak" fad. But if you see a funny picture with the caption "Im in ur foldur keruptin yr fylez" you know this is not meant to be "good" English but just a humorous interpretation of how cats would talk, if they did talk.