Can i buy an australian nintendo and play in europe?Do they have the same region code?

You can, EU and AUS are considered the same region by Nintendo.

However - living in AUS, I imported a US 3DS and wouldn't recommend anything different. Games come out sooner in the US and they're about the same price if not a little cheaper factoring in the slight surcharge you pay for getting 3ds store cards online from playasia etc. Heck, SMT4 isn't even out here yet. Seriously, it's been a year.

Until Nintendo get their shit together and make their consoles region free and import friendly, the only smart thing to do as an English speaker is to get a US 3DS. That is, unless warranty and physical copies are important to you.

Thank you :)