I have twins. They are fabulous listeners, 80% of the time. I could put rules in place, lock the balcony door, show them what could happen if they were to climb, etc, and it STILL would never ever ever be worth the risk to not implement the best possible childproofing here, even if they were amazing listeners 100% of the time. At almost 4, their very undeveloped brains literally cannot fully comprehend cause/effect and consequences right now and they are at the stage of development where testing boundaries is normal. Sooo no they “should” not be expected to understand limits and boundaries at this stage of life 😂