For about half a billion years Earth was mostly molten on the surface. So about 11% of the time. And then we've had major glaciation periods especially the cryongenian that lasted 78M years about 640M years ago.
Is there a reason why life HAS to evolve on an earth like planet? I guess it's the most likely given our experience, but could life happen on Venus or something?
We only have one planet with life on it to go off and finding life is like looking for a needle in a haystack. So while other exotic forms of life may exist, it would be a lot harder to search for and recognize. And the conditions under which life on Earth exists are understood better so we can look for those range of conditions rather than aimlessly search every conceivable but less likely set of conditions. eg. liquid water. Life can survive two of the extremes of acidity, salinity (saltiness) and temperature but not all three (that we know of) and there has to be a chemical and/or energy disruption of equilibrium of the system. eg. CH4 in the presence of O2 etc. In the needle in a haystack analogy, we are using a magnet to sift through the haystack first because needles that we know of tend to be magnetic. If we dont find anything we might search for bone or ceramic needles using different search methods etc.
From my understand (degree form YouTube), our understanding of what is needed for life is liquid water and free energy.
Which means earth like is most likely, but there are other alternatives. For example, the moon of Jupiter (Titan iirc) is ice covered but has liquid water beneath the surface, and the gravity of Jupiter should provide the free energy so that’s the Vegas favourite for finding extraterrestrial life within our solar system.
In part because we need better ways to measure the contents of the atmosphere of said planets, we basically can't right now (but some gas giants), whenever we can, we may find life, or not, but it will be interesting.
The closest Earth-like planet to Earth is Venus. It's located in our own solar system and shares many similarities with Earth, such as a comparable size and mass. However, its atmosphere is much denser and consists mostly of carbon dioxide, making it an inhospitable environment for life as we know it.