Yes, we're quite aware that this is a controversial topic every year. And you are correct in that there is a limit to how much the field designer can expect from the team.
The reason why this hasn't been clarified in the rules and has always been vague is because it is just impossible to come up with a generalised rule without any edge cases whilst allowing the field designs to be versatile (so once again I can only answer in a "general" sense, and the specifics are tbd by the local field designers).
So for your 3 scenarios:
• Scenario 1:
Yes, I think the robot should be able to detect this.
• Scenario 2:
This is a tricky one. In general no. We are not expecting teams to detect ramps in this way, so in theory field designers shouldn't deliberately make a course where the robot must recognise this scenario. But that doesn't mean obstacle paths and ramp locations can be in proximity. If you're robot just so happens to be excessively huge, and as a consequence must detect the ramp to move the other way, this can be a situation where the course can be unchanged.
• Scenario 3:
No. (I mean if you're team can create such a system, it can also be used for other purposes so go for it!!)
At the end of the day, this whole "premapping" rule is not in place to raise the difficulty of those that are tackling the rule with respect, but to penalise teams that are trying to cheat. At least in the international competitions, if you feel like the field designer is taking advantage of this rule and covering a legitimate team, you can probably argue for a change.
Does this answer your question?