No Problem to do this, but there are really no amplifiers with an output impedance of 8 ohms on the market. All loudspeaker amplifiers have an impedance of less than 0.5 ohm.
Scroll down to related links and look at "Impedance bridging - Wikipedia".
You can connect 8 ohm speakers to a 2 ohm amplifier, but you are not going to achieve rated power. It is better to use the exact speakers designed for the amplifier.
Two 8 ohm speakers in parallel is 4 ohms, and the power will be split between them.
However, unless the amplifier is rated for 4 ohm operation, you will not get the same total power out of the...
If you mean as pairs, yes. put an 8 Ohm and a 16 Ohm speaker in parallel for each channel. The 16 Ohm speakers will take 1/3 the power and the 8 Ohm speakers will take 2/3 the power. The resulting...