Given scene/plot descriptions from movies or TV shows, and given a specific question about the scene, summarize the question into a title

At the end of Stranger Things' second season, we see that    Will uses Morse code to secretly communicate with Hopper while the monster is possessing him.  Why does Will know Morse code? Did I miss something? Hopper and Eleven know it, Hopper due to his military training, Eleven due to being taught, but Will just doesn't seem to have any particular reason to do so.
Why does Will know Morse code?

In Justice League, we got to know that Steppenwolf already tried his plan in the past; and the combined power of Amazons, Atlanteans and humans defeated them. But there were others involved too, some major DC characters, one Green Lantern (not sure which one), Zeus and someone with fire arrows and a few more.   So who were these heroes with powers? Are they some DC comics characters? I can identify Zeus but not the rest.     Who was the Green Lantern, that died, in that fight?
What were all the fighters in previous Age of Heroes?

Doc Brown has got a time machine, why is he in a hurry in the end of Back to the Future part 1? Why doesn't he just give a parenting lesson to Marty?  A little more context: At the very end of part one, doc goes back to Marty to tell him about his son which is going to jail in the future and they need to stop that to happen. He is really in a hurry, but c'mon, you can wait a couple of days in the present then go back to the future at the very same moment he intended to go in first instance. He has plenty of time to achieve that!

Why is Doc Brown in a hurry in the end of Back to the Future part 1?

