Yes, you can absolutely activate a creatures ability before it dies, assuming that you can pay the costs
Rakdos Midrange (2 players): Rakdos Midrange puts together the most efficient interactive spells, creatures, and value engines available in black and red
Betrayal Whenever a legendary creature with counters on it dies, draw a card for each counter on it
This does not include other card types that produce mana as an ability
Forget what people have told you about Mind Twist and Ancestral Recall, because neither of these cards dominated the way that Balance did when people were allowed to play four per deck
An artifact's mana value is determined solely by the mana symbols printed in its upper right corner (unless that artifact is the back face of a double-faced card, is a melded permanent, or is copying something else