tannins can leach for weeks to years ~ if you don't mind the yellowish color which isn't harmful to fishes. it depends on your preferences. but boiling it or soaking for a few days will remove the tannins,but not all.
Excellent. I love driftwood in a tank. I have done that too (boiled and let it sit submerged for days as well), but I was lucky with the color (or more likely I didn't notice.) As long as it doesn't actively discolor the water it's in (much), it's just a matter of taste.
It just stinks that most people assume anything but clear water means bad fk
My piranhas had clear water when I first got them but it just looked un natural to me, and after I did that they were much more content imo. Plus not as much lite can penetrate the tank, thus no more algae.