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We must have some idea where the planets were back in the time of dinosaurs. I mean, Earth was still approximately the same distance from the Sun, and presumably still #3 right?

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Probably the order of the planets was the same but we can't be sure of the eccentricity of their orbits back then. We do know Saturn probably didn't have rings back then.

"We have no idea where Venus will be exactly [ten] million years from today."

I'm trying to figure out what this is supposed to mean. Of course we don't know exactly, but also of course we have some idea.

Like, could Venus have had an eccentric orbit that extended further from the Sun than Earth or closer than Mercury? Could it have had a moon?

Sorry I should have been more specific. We can't predict the accurate position of Venus in its orbit ten million years from now, and it's possible its orbit will have a different shape then too. However it's unlikely that the orbit would be so eccentric that it would intersect with Earth's orbit. That kind of deviation becomes more likely when we talk about a billion years.

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