My questions:
- Is what ChatGPT said correct, especially for explanation of sentence 1?
- Is there any main difference between sentence 2 and 3?
- Which one would a native speaker normally say?

From ChatGPT:

Sentence 1: "The game has been free for years until today."
Tense: Present perfect.
Meaning: This sentence is awkward. It implies the game is currently free but contradicts by saying “until today.” A better phrasing would be, “The game has been free until today, but now it is not.”

Sentence 2: "The game was free for years until today."
Tense: Simple past.
Meaning: The game was free for years, but this has changed as of today. It suggests that the game is no longer free starting today.

Sentence 3: "The game had been free for years until today."
Tense: Past perfect.
Meaning: This indicates that the game was free for years before today. It suggests that the free status has ended today.