That's a problem. Some people upload themes without telling it's v4. Some have v4 in their name, but that could of course also mean version 4 of that specific theme. Themers should declare that in the upload title or at least in their comments.
Your best bet is look at the screenshots. There are some clues that reveal v4. Eg, if any of this is true:
- docked windows on the left/right/top of the main window
- toolbar buttons docked at places other than the main toolbar position (often v4 screenshots show that long toolbar all across the top of the main window.
)
- Buttons on the track headers or the mixer channels are in a different position than you are used to from v3
- faders on different tracks have different colors
- track headers/mixer channels clearly differ from each other in their layout
you are looking at v4.