The answer depends heavily on how you define information, but generally "no useful data available."
One key point: much of what will happen over 25MY is stochastic -- random. If you need to say "this body of 100kB survived perfectly," then there is virtually 0 chance it does, no matter how it was stored. If you relax that to "some random X% of the data survived," you can start to keep things for long durations.... it just wont be easy.
25MY is a geologic timeframe. You're talking about the difference between the earliest dinosaurs and now. That's a beast of a timeframe and a lot can happen!
The biggest focus I would have is on the spatial frequency of information. Right now, humans are compressing their data onto things like hard drives, which store information in microscopic regions on a metal platter. Storage in small areas like that is rated on the order of 10-50 years. Books, despite inferior building materials, are still readable a thousand years later, mostly because they store the data in a larger format. Clay tablets last even longer, as do stone inscriptions. The larger the medium, the more it survives.
If we are talking about a timeframe similar to that of the dinosaurs till now, expect significant sediment to gather, and do so slowly. Everything humans will have done in our entire civilized era will be compressed into a layer a few millimeters deep. The surviving things will mostly be the few things that were not broken or oxidized before getting compressed into oblivion, and then torn at with forces strong enough to sculpt the Fjords of Norway (which, is believed to have occurred no more than 0.1MY ago).
But what if civilization is actively trying to preserve data?
What if the civilization undergoing Armageddon is actively trying to preserve its data for 25MYa? It could not preserve much.. the forces of geology are unrelenting. However, if it is a small bit of data, say the name of the Archangel which destroyed the world, there's a chance. The trick would be getting the signal to noise ratio high enough to survive the random effects of geology (we're assuming geology is not an intelligent adversary actively seeking and destroying data). A small amount of data could be replicated over the entire earth, in hopes that things can be stitched together. This would effectively be a Raid 6 storage array on steroids.
However, we would have to find the data, and know where to look. Something replicated that many times would look like a curious noise pattern. We would need to clue the next civilization in.
*(Note: I'm calling the the next civilization. I think it is fair to assume that in 25MY, the progeny of humanity will be so unbelievably different, both in shape and in culture, that we might as well treat them as an alien race)
One solution which seems legitimate is fractal encoding, where the same message is encoded at many different sizes. This would be an effective process for saving information like that because it is reasonably likely that the next civilization would be looking for life, and that kind of pattern is really hard to arrive at without life on that planet. They'd be looking for A message, and would hopefully find the message we are looking for.
The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...' - Isaac Asimov
The final challenge is linguistics. We lose languages in hundreds of years with ease. Making sure the message is understandable when we return 25MY later is a challenge on par with the Voyager Golden Record. How you overcome that difficulty would be on you.
Your final question about mixed technology really deserves its own question, because it is MUCH less related to information storage. However, generally speaking the answer is no: you do not see technological gaps like that. Engineers and scientists and inventors are just to bloody creative. They will dismantle what it took to learn to construct a rifle or a holoplayer, and rapidly apply that technology to everything. It will not take long to "fill in the gaps." Just look at how rapidly western technology ripples through a primitive culture over the course of 50 years, much less 1000 or 25000000 years.
"Inspiration unlocks the future; technology will catch up" - Caproni in
The Wind Rises by Miyazaki.
The one exception that I see would be Arthur C Clarke's definition of magic. If the new tech is so unbelievably advanced, it would be indistinguishable from magic. This would protect it from the prying eyes of the curious. However, it would also mean the only advanced devices would be those which survived from 25MYa, because they wouldn't be able to create new ones. This puts us right back at square one: keeping something intact for 25MY is hard!