Extract the zip to "Steam/steamapps/common/Street Fighter V".
SFV has a bug where one player's game can lag behind the other's online. This can cause artificial lag and one sided rollback for the other player.
When the players' "clocks" are synced, if there is e.g. a 4 frame packet round trip time between them, each player should be 2 frames ahead of the time of the last received input from their opponent, and experience 2 frame rollbacks.
If one player lags behind, the other player will receive inputs from farther "in the past" (up to 15 frames!) than they should, causing unnecessarily big rollbacks and artificial lag, while the player that's behind may even be receiving inputs that appear to be "in the future" to their game and never experience rollbacks at all.
This fix ensures your "clock" never gets more than half of your packet round trip time ahead of your opponent's so that you never experience more rollback than them.
No, but if they don't have the fix, it's still possible for them to experience one sided rollback.
This took a bit over 2 days to make, while Capcom hasn't patched the bug for 4 years. Most of that was reverse engineering. It would take more like 30 minutes with the source code. MikeZ even made a tweet pinpointing the cause of the bug during the beta.