Does evolution/other modern scientific theory say anything about...?

Evolution just says that things which are more likely to reproduce tend to reproduce more, and this is why we see organisms evolve over time. Namely, they evolve because traits which allow them to reproduce more are more likely to be passed down and thus more prevalent in future generations.

It holds in any case where a lifeform can approximately reproduce itself with some variations through its offspring and traits can be passed down.

No.

It does say that evolution proceeds in a series of steps, some of which are very small changes, but every change must give some kind of ecological advantage. It does sometimes mean lifeforms can take dead-end paths (like the dinosaurs as extremely large beasts).

And, even of earth, although we think of it as an oxygen-rich planet, it wasn't so before 2.5 billion years ago, and life did form more than 2.5 billion years ago, albeit most microscopic and anaerobic.

Could those anaerobic life forms developed further? Probably!

So, our observations and discoveries are primarily for earth, because that's what we are closest to. But the idea of evolution for fitness applies to other possibilities as well.

Since we have no examples of planets with life on them you won't have a pronouncement from science until that happens. All we can do is speculate. Even if we knew there's life somewhere else, which is likely given the size of the universe, we have no idea if their chemical composition, and interaction with their environment is similar to ours. If it was the same, then yeah, I guess evolution would apply there as well. If certain organisms survived better than others under certain conditions, and passed on some kind of hereditary information to their offspring evolution should happen since there will be changes throughout generations on a given population. That's all evolution is.

But then again, who knows how life might look like in another galaxy. What if there's a planet with only giant fungus-like creatures with no DNA, or RNA or anything like that (no mutation) that only need light to survive so they don't compete for food, they replicate themselves to reproduce by who the hell knows, and are immune to any pressure from their environment. They don't get sick, and nothing in their world can kill them. They just die after they become 500 years old and only after they've created copies of themselves. Evolution as we know it wouldn't happen there, but as you can see the possibilities on ridiculous scenarios are endless, so it is kind of a useless exercise without actual examples of extraterrestrial life.

The evolutionary process on earth is not even a consistent process. It was just a couple of years ago that an "arsenic" based life form was discovered and I believe it was last year that a life form was discovered that did not need or use oxygen in anyway.

Those were both discoveries that would have been thought "impossible" just a decade ago. Basically the formula for life is one that science is not even close to cracking. The source link I posted points to the article Washington Post article talking about the arsenic life form.

There's lots of speculation and philosophizing about it, but without hard data, it's all just so much hot air. We won't know for sure until we go look.

By the way, joshua, that arsenic life-form thing was thoroughly debunked within days of its publication. It was a horribly, horribly done study that never should have been published. The authors made some huge mistakes, and have essentially lost all standing in the field. It was a nice example of science correcting itself.

It is logical to expect that evolution would work on all living things, even alien life forms, but, so what!. To the best of our current knowledge, the only place that life exists in the ENTIRE Universe is here on earth. So... it is interesting to fantasize about such "what if" questions but, until we actually find a form of life somewhere else, it is not really worth spending much serious time on because there is no actual science we can do on it.

If life there had a chemical basis similar to our RNA / DNA, then yes. Natural selection would happen in any environment. But for the evolutionary biology we know, reproduction would need genetic properties somewhat similar to ours.