Can you help me understand the conclusions of the double slit and the delayed choice experiments?

Well first of all, is there one true conclusion or are there just several hypothesis on the results?

Why do they attribute the delayed choice results to a time travel rather than an unknown variable in the photons behaviour?

I see that "observing" a photon is actually interfering with its behaviour, making it go through one slit instead of both, but what if it doesn't go through both slits when unobserved, what if there's another movement pattern that could be congruent with an interference pattern?

Or, what if the photon isn't actually a photon before interacting with something? Could it be something else entirely which, when colliding/mixing/interacting with matter becomes a photon? And so could its velocity be different from that of c? Giving so the illusion of time travel?

If the "observing" telescope could register pattern of absorption, could it be an interference pattern? If so the photon hiting the screen would be a secondary hit, giving it distinct properties?