How would the physics of those three observations work, and what angular resolution would be required? I can see spectroscopy working for #3 and #2, #1 stumps me.
In theory #1 could be answered by looking for an atmosphere temperature that are similar to Earth’s despite being in an orbit that should make the planet cooler. If there is no plate tectonics then all the CO2 gets locked up in carbonates and the temperature falls (e.g. Mars) or you get a run away greenhouse like Venus. It is plate tectonics that have kept earth in the habitable zone. In theory we should be able to detect such a temp delta.
