Alien curiosity

I’m just curious about this one. When you try to copy an Alien movie from the quadrilogy box set in movie only, what version do you get?

I just remembered that on these discs you can choose what version of the movie you watch i.e. theatrical version or directors cut. I was just wondering how the hell they did that. The layer break happens at the same point on both versions so they didn’t compress the disc to have two movies, one per layer. Is the dvd technology really that good that the laser can seamlessly jump around the right scenes? I never believed that it was.
My old laserdisc machine moved much faster when you clicked on what you wanted. I have (on dvd) an old 80’s arcade game called Dragon’s Lair which is a disney - like cartoon movie that pauses whenever you make a move so the dvd can go to the right scene.
The laserdisc’s reaction time was much faster and so the movie played perfectly until you made a wrong move. Only then would it pause and go to your death shot. The dvd pauses whenever you make a move regardless and so is not as fast as the old school technology playing each scene full of little interruptions as you play it.
With this in mind it amazes me how these Alien discs perform so well.

anyone know how they got both versions on the disc like that?

Alien is an example of interleaved multi-story DVD, in which you can choose which version to play at the start of selection, not during. Similar scenes are used by both versions and then seamlessly branch to either version and back to similar scenes again, and so forth.

Only high end professional authoring software is able to do this task so your dvd player is able to recognize such structure and plays seamlessly.