How can I get this glass stopper out? Need troubleshooting!
I found gently taping a glass stopper with another glass stopper sometimes loosens it(maybe the shock is allowing air to pass through), but you could always put ice on the stopper and surround the top of the flask with warm water and wait a minute or two. This allows the top of the flask to expand while the stopper shrinks just a bit. Then, just take the stopper out. If you lose all hope (I hope that doesn't happen) and don't care about about your solution I would just use WD-40.