Your assumptions and examples are mostly correct. Here’s a concise explanation and clarification: Earlier: Can be used for both past and future events. Example: "The red bus arrived 2 minutes earlier than the blue one." Sooner: Generally used for future events, often implying a preference or urgency. Example: "The red bus will arrive 2 minutes sooner than the blue one." Your examples reviewed: Past event: "The red bus arrived 2 minutes earlier (not sooner) than the blue one." Correct: Use "earlier" for past events. Future event: "The red bus will arrive 2 minutes earlier/sooner (both work here) than the blue one." Correct: Both "earlier" and "sooner" can be used for future events. Past hypothetical: "I wish we had met an hour earlier (not sooner). Then we would have had enough time to grab a drink together." Correct: Use "earlier" for past hypothetical situations. Future event rescheduled: "The meeting has been rescheduled for March 10th, so it will take place two months sooner/earlier. (both work here)." Correct: Both "sooner" and "earlier" work, but "earlier" is more common for scheduled events. Guideline: Use "earlier" for both past and future events. Use "sooner" mainly for future events, often when indicating a preference or urgency.

I am a native speaker from the middle of the United States. Both words are understandable in your examples. In my opinion, I'd say that, "Sooner" is a more casual word. It would be more polite to use "Earlier". Example, as spoken to a close friend: He keeps getting there sooner than the rest of us. He gets the best parking spot. Example, as spoken to a guard or to your supervisor: He arrives earlier than us. He can, therefore, select the best parking spot.