Yes, the bounce height will vary based on the length of the bungee cord. A longer bungee cord will result in a higher bounce height because it allows for more stretch and potential energy to be stored before the rebound. Conversely, a shorter bungee cord will have less stretch and thus a lower bounce height.

gravity will make you bounce higher because as cord gets longer the more force it will take to move it.

Yes. The farther down gravity pulls you the farther you'll go back up.

No.

Although many things hurtling through space DO bounce off of the Atmosphere and the Stratosphere, you cannot stick a bungee cord to the stratosphere and jump off, the cord would fall along with you, and you would die.

You can elasto blast into them at an angle. You'll bounce along without having to do any extra work.