Yes, if you mean a "normal" audio mixer with e.g. XLR outputs or Jack, that is possible. But I would rather recommend the interface 2i2 so that you can process the stereo signal or just make sure that it is mono:)

I assume you mean something like an MPC?
You can't do much with a mixer alone.
so connect the mixer mpc to your pc and then connect it to your audio interface.
basically i would always ask youtube, you can find everything there :)