Soudal 750ml Champagne Gap Filler Expanding Foam Handheld Spray with Nozzle & Gloves (3)

can it be used to fill in the void between stairs and plasterboard below when insulating for sound?

how difficult is to remove it after it dried?

Want to fill a gap between a board fitted to a chimney flue to stop debris falling down. Will this drip down or does it harden quite quickley?

What colour is it