Yes. An awful lot of evolution is possible in 100 million years.
Consider your question in the context of it being asked slightly differently by an intelligent alien visiting Earth 100 million years ago. At that time there existed a family of small, unintelligent, timid pre-rodents called multituberculata, the last common ancestor of mice and humans. Your visiting alien finds one and asks, "could these develop into intelligent spacefaring bipeds who dominate the planet in 100 million years?"
The answer is obviously "yes" because that's what happened. But if you took a parallel universe machine and re-ran the history of the Earth over and over again from that starting point 100 million years ago, is it likely that that's where evolution would have gone by the present? Probably not. It could be really unlikely that's where evolution would go over those 100 million years. But the anthropomorphic principle applies: we're in the universe where it did happen, so we're here observing that it did happen, so of course it doesn't seem very unlikely to us.
Evolution isn't a nice linear process where we can look at an octopus and say that's where it's heading in 1, 10, 100 million years. It's mainly driven by extinctions: whatever favours the diversification of octopuses probably simultaneously made a lot of the competitors for niches they might fill extinct. Allow a good mass extinction or two in your 100 million years and if octopus-descendants survive who knows how their descendants would adapt. If they adapt to breathing oxygen there's a fairly immediate fit into a sort of predatory amphibian niche living in swamps but over that length of time you could see fundamental changes with entire limb functions changing like the development of wings in early birds, changes in skin type and so on. Octopuses today are very likely more intelligent than the primitive euarchontoglieres that were the last common ancestor of mice and humans 100 million years ago, so in another 100 million years who's to say they wouldn't evolve into land-dwelling, air-breathing sapients capable of similar feats to modern humans?
A version of the anthropomorphic principle applies to evolution in your world building: even if it's a very low probability evolutionary path, if you want it to have happened then it did, because the world where it did is the one where you as the author choose to set your story.