Out of the box, no. The Nintendo 64 has a region lockout chip which prevents NTSC (Japanese and US) games from running on a PAL (European) machine.
However, through the use of third-party devices, most games should work. I personally own a N64 Passport Plus which I use to play Hey You, Pikachu! on my own N64. It basically works by using a second, local cartridge to authenticate with the lockout mechanism.
I don't have first hand experience of this, but according to that Wikipedia article, some games won't work even with this - presumably, they perform additional hardware detection, so they might be hard to do anything about. It may be possible to somehow bypass these through Action Replay codes; I don't know exactly how these games perform those checks.
You could also buy a Japanese N64 and bring that home. You'll need a power converter to make it run on 230V, and a TV which will accept the input, but you could run any Japanese game that way, and any US game if you remove the plastic tabs.
As an alternative, if you have a European Wii, at least some of the games might be available on the Virtual Console, saving you the trouble of messing with adapters.
Yes, what you want to do is possible. While all 3DS software is region-locked, Nintendo DS software is not. Because that region-locking isn't encoded into the DS software, you can play software from all regions on your 3DS.
You can even check out this youtube video where someone demonstrates a DS games from North America, Japan, and Europe on their North American 3DS.
Best Answer
You can actually know not just the region, but often the individual country the game was released in.
Look near the barcode in the lower right on the back of the case. You'll see a code like
CTR-APPP-GERorCTR-A66J-JPN, maybe withTSAbefore it, or a similar code with aPin the middle likeCTR P ATHE USA. The last three letters indicate the country of origin withASIfor multi-country Asian releases.This is the same code that's on the cartridge itself, though that one will be prefaced with
LNArather thanTSA, and won't have aP.