1) How long it takes would depend on the type of portal! The truth is, we don't really know if these portals exist, and if they do, what do they do? Some people speculate (meaning they make a sort of "wild" guess about something we can see but don't really understand) that black holes might be ways into other universes/galaxies, and things called wormholes might be another type of portal for this kind of traveling, but we don't know if any of this is true. We only know that black holes exist; and we don't even know if wormholes are real.
2) The "diamond" planet you're thinking of is called 55 Cancri e, but we don't know if it's made of diamond. It's so far away that we can only measure and calculate very little of what it is, such as what its atmosphere is made of or how big it is. The "diamond" is a possible explanation of what we can see in the planet's atmosphere, which means that we have to guess a lot in order to get to the explanation that the planet is made of carbon in the form of diamonds.
3) The darkest planet that you're thinking of is called TrES-2b, which reflects less than 1% of any light that hits it, so it looks very dark to us. By contrast, the Earth reflects about 30% of the light that hits it.
The water planet you're thinking of might be GJ 1214b, but again, we don't know if it actually is made of water, just that it could be an ocean planet, or a smaller Neptune (with a thick hydrogen-helium atmosphere), or something else.
4) There is a list of interesting planets on the NASA website: click here. Again, we have a lot of guesses about what things exist on these planets, but very little evidence because they're all so far, and we can't reach that far yet to look. Also, this list only includes 20 of the more than 4,000 planets outside of our solar system, and those are the ones we've seen, so there are many more we have not seen and don't know about. I won't list all 4,000 names here, but some of these planets are interesting because they might be able to support life like our planet, and others are interesting because of how hot/cold they are, what might be on them, and what they can show us about how planets form.
5) If by "planet like Earth", you mean that it has an atmosphere and the right "stuff" to support life, then we know of a few rocky ones that are not too far or too close from their own suns, but they are probably all too cold or too hot to be like Earth.
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