I think aliens capable of interstellar flight will be humanoids. Not necessarily based on primates; they could be feline, canine, anteaters, lizards, Zuckerbergs, whatever.
We clearly have the best form for tool use. If some drastic difference in morphology made for more efficient tool use, we would have evolved that form. Tools are very much our jam, got us where we are today.
I also think they would be from a biosphere much like Earth. They evolved under the same physical and chemical laws. Sure, there would almost certainly be radical differences in biology, but I think we'd recognize the basic building blocks. After all, amino acids are floating around in space.
OTOH, maybe they've evolved so far beyond tool use as to be unrecognizable to us. Maybe they use bots for tools and artificially modified themselves.
As to your penultimate sentence, that's a plot point in science fiction classic Footfall!