Are these perfect IVs Dittos?

Question

I play Pokémon White 2.

I've began to start breeding all my Pokémon for ideal natures and perfecting EVs. Then I read about breeding for IVs, so I Googled about that. Going off of what I read and was able to comprehend, I went to hunt for "perfect IVs Dittos." I was still unsure about how to determine if one had perfect IVs, so I focused on just catching Dittos with natures that I'll be needing. I then went on an IV calculator and filled in the information for five Dittos that I've caught. The guide I read was Azurilland's, and the calculator was from that website too.

Correct me if I'm wrong: All Pokémon can have perfect IVs in one stat?

My main question is this: If I input all the information (minus hidden power, is that relevant?) of a Ditto into an IV calculator, and one of the results say "31," does that mean the Ditto has perfect IVs in that stat? 2 out of 5 of my Pokémon had 31 in a stat.

Screenshots:
One Ditto
Two Ditto

Side question: If I bred two different nature Dittos together (neither holding an Everstone) will the resulting Ditto have its own nature, or will it be a parent's?

Answer 1

Yes, it seems that your first Ditto has perfect Defence IVs and that the second one has perfect Speed IVs. Cross-checking this with Pokemon Showdown's teambuilder verifies that the calculator is indeed correct in each of its estimations, assuming that neither Ditto has gained any EVs. 31 is the maximum amount of IVs Pokemon can have in one stat. Just be careful using the term "perfect IVs", as this is generally used to describe Pokemon with flawless IVs in all of their stats; there's no limit to how many perfect stats a Pokemon can have.

Hidden Power type is helpful in finding the IVs of Pokemon, as the type is determined by the same numbers. It's relevant and will narrow down some of the numbers for you, but quite clearly it's not absolutely necessary to make good estimates of IVs. If you're interested, you can find your Pokemon's Hidden Power type by checking with one the people at the stalls outside the PWT, then input the type into Azurilland's calculator.

Also, it's worth mentioning that you don't need to use an IV calculator to find out if your Pokemon have perfect IVs, as there's a way to do that more quickly in-game. If you've beaten the Pokemon League, an Ace Trainer will appear in the Gear Station at Nimbasa City, who will evaluate your Pokemon's stats. He will tell you which stat has the Pokemon's highest IV, and if he says that any of your Pokemon's stats "can't be beaten", then that stat is perfect. If there's a tie (and if there's more than one perfect IV), he will suggest that the other stat/s are also good. His descriptions of the IVs are vague and unhelpful otherwise, so if you want exact values for all of your Pokemon's IVs, a calculator will be more helpful.

For your side question, the only way to guarantee natures when breeding is with an Everstone. The baby will have a randomly generated nature based on its personality values.

Answer 2

My main question is this: If I input all the information (minus hidden power, is that relevant?) of a Ditto into an IV calculator, and one of the results say "31," does that mean the Ditto has perfect IVs in that stat? 2 out of 5 of my Pokémon had 31 in a stat.

Yes, that is what that means.

(minus hidden power, is that relevant?)

Hidden Power is a very unique attacking move in Pokemon. It's type (and before X/Y/OR/AS, also it's power) is determined by the combination of odds and evens in the Pokemon's IVs. Knowing what type (and in your case, power) of Hidden Power is just an additional data point for further narrowing in the specific IVs of the Pokemon in question.

Correct me if I'm wrong: All Pokémon can have perfect IVs in one stat?

There is no limit to how many stats a Pokemon can have perfect 31s in. However, it is usually very rare for a wild Pokemon to have more than 1, or even 1 at all. Usually you have to exploit breeding tactics and items to manipulate them to get "perfect" Pokemon. For example, if either Pokemon in the Daycare is holding the Destiny Knot, the child will directly inherit 5 of it's 6 IVs (chosen at random) from one of it's parents (again, chosen at random).

Side question: If I bred two different nature Dittos together (neither holding an Everstone) will the resulting Ditto have its own nature, or will it be a parent's?

For all breedable Pokemon, the absence of the Everstone will result in the Nature being chosen at random. However, Ditto cannot breed with themselves.