1. no.
2. make something with keys target, target2, target3, target4 if u need to target multiple things,(<- AMP only) or just use same targetnames for what you want to trigger. You can make a button trigger a speaker that plays once, and a 20s delay that at end will trigger other speaker that has looped_off spawnflag set.
3. Make a brush into trigger_multiple, apply trigger texture all over it and you have a zone that can trigger stuff.
4. Make it trigger a target_relay with human/alien_only spawnflag set which then triggers the target_speaker.
5. Ofc it is, why not? just make 2 target_speakers.