Can I play Cake Mania 4/Word Searcher 3 or will I get lost if I haven't played the previous 3/2?
The long-awaited 3DS system update is due on the evening of June 6 Pacific time - it will include accesss to the eShop, as well as the internet browser. And I think you lose your OK Go video from the last update, so watch those dogs jump around in 3D while you still can.
With the Pokemon games historically, there hasn't been a great reason to get the matching release. I don't know that this has changed or not, though. Generally you just needed to find someone with the other version and trade some Pokemon with them.