Classic, Time Trial, and Mystery are named options, but their differences should be read from the game rather than filled in from genre expectations.
Use mode names as starting points
Water Sort Master advertises six modes and names Classic, Time Trial, and Mystery. Those labels suggest different experiences, but the stored record does not finish their rules or identify the other three modes. Open the actual mode information before choosing. Your useful question is which option supports the kind of session you want: deliberate inspection, decisions under an explicit timer, or another variation that the game itself explains.
Keep the sorting objective separate
The supplied task is sorting colored liquids until each flask contains one color. A mode may change the conditions around that task, but do not assume it changes every pouring rule as well. Read the visible constraints and feedback. Comparing modes becomes clearer when you identify what stayed the same about the sorting goal and what the chosen option actually added, removed, revealed, or timed.
Compare your decision process
If you try more than one mode, note how the rules alter your attention. Perhaps a visible timer limits how long you consider a pour; another mode may ask you to inspect different information. Those are observations to make, not promises about the named options. Judge the mode by whether its real rules match the thinking you wanted to practice, rather than assuming the most mysterious name must also be the most difficult.
Arcade