No it’s not possible, as I recall froakie and litten/oshawott (depending on whether you’re team magma/aqua) are only available after the main game story in agate.
As for the topic, just click the forum you’d like to drop your question in, then add the topic by selecting the ‘start new topic’ (iirc)
If you don't have a problem moding, you can use the shared PC mode that lets you trade between save files. I got all the starters except turtwig and had to trade myself that on. (screw those puzzles)
