It is a good game. Yes there is online, but I always have trouble finding matches with other players. I’m sure I will find more online matches when the game gets released worldwide. It has a good balance of single player & online modes.
There are two modes for online (ranked games & groups). Ranked games is where you play one event against other players. For example the 100m can have up to 8 players for online. For Beach Volleyball you are playing against one other player. You can also play with your friends or with other players in a group format (up to 4 players). You can pick the events you want to do & those events will be contested between/with the players in your group.
For single player/offline there is a practice mode where you just practice the events. You can also play an offline Olympic Games. You compete against the computer in an event of your choosing. For example, in the 100m you do a qualifier, then if you get top 3 you advance to the semifinal than final. The level of difficulty gets higher as you advance. So far I have won gold in BMX & silver in beach volleyball.