Malevolent Whispers - attacking and effects?

Bluezeak

I've tried to use this card several times, but I've never been able to attack using the creature I control.

If the creature is summoned, and I immediately take it while it's still disabled, then I assume I can't use it because it's disabled.

But if I take it on the next turn, after it's gotten the chance to attack one time, I should be able to attack with it, right?

Also, I took control of a creature that gives life when it enters the battlefield. I don't remember which one, sadly. When I obtained it, I got no life, but when my opponent got it BACK from me, my opponent got life a SECOND time - is that working as it should??