Would a 2 amp audio amp get damaged by a 10ah battery? (im new to this kind of stuff)
For your first question:

You seem to be confusing Amps with Amp-Hours; these two are somewhat related, but really are entirely different units of measurement. Electronic devices will often have a current rating, noted in Amps, and a voltage rating, noted in Volts. The current rating marks the amount of electric current drawn by that device under normal operating conditions. You will need to power that device with a power source that is rated for an equal amount of voltage, as well as an equal or greater amount of current.

Amp-Hours, on the other hand, are a measure of battery capacity. A device rated for 10 Amp-hours can source 10 Amps of electric current continuously for 1 hour before it needs to be replaced or recharged. In the context of your example, the 10 Ah battery will be able to power your 2 A board for 5 hours before it dies.

For your second question:

It would be nice to have more detail about the specific amp and speakers that you are using, but the likely answer is that there will be a potential for damaging your 12 W pair of speakers if you connect them to a 100 W amp. That being said, your amp's 100 W rating specifies the maximum power that may be achieved by that amplifier for a certain impedance load; this means that operating the amp at a low level should allow your speakers to operate without sustaining damage. Just remember that there almost certainly will be a potential for damage to those speakers if you aren't very careful with the gain knob.