I agree. Everyone who plays the game will make mistakes. But that's the point of the game. To build upon your mistakes. Without that "Revert to VAB or SPH" option, it makes it un-playable. Only work around I figured out for now is simply saving before entering the VAB and editing the Start Node of the mission to have the VAB unlocked all the time.
At least I finally got to the ending of "Dawn of the Space Age" using these methods. Look up the "soyuz rocket engine" for building the rocket. Besides making the sputnik satellite. I am now trying to figure out how to get the rocket in orbit, problem is the launch location is near the pole of the planet. The target orbit is at the equator of the planet.
Without SAS on the sputnik probe, flying this stuff feels like your flying with a elephant pull you around. Thinking of just modifying the probe to have it to make it easier for myself.
EDIT: I don't know how this work, took a gamble at it. Had only a small amount of delta v left in the rocket, like 300, 3 tanks. Added a maneuver where the target orbit and the current orbit match up. 50 sec burn or so. Did the burn, empty the tank. Only a little bit to go, so launch the probe, got it into the orbit. Unfortunately the game is not detecting that I achieve the orbit, not that far off from it
EDIT: Guess I had to lower my orbit below 100,000 for the game to detect my ship. Also had enough fuel to de-orbit the satellite and have it burn up.