Board Thread:Theories and Speculation/@comment-32742265-20180119154238/@comment-26107879-20180209035854

First, does everyone possess the ability to use any nature as long as it isn't Kekkei Genkai (For example, can an Academy Student with a Fire Release Affinity, learn how to use Water Release if he is trained under it)? If so, then next question.

Second, are hand signs the way a Shinobi manipulates their Chakra? If so, then next question.

If anyone has the capacity to learn any nature minus Kekkei Genkai, and they can perform the Hand Signs necessary to perform a Jutsu as long as they have the necessary Chakra to do so, that would mean that a Sharingan User can indeed, copy any jutsu they see, right?

Of course, just cause they know how to do what is required, doesn't mean they possess the skill to do it. For example, you see someone do a back flip. You seen everything that went into it, but you might need to practice before you can do it. You just don't magically become flexible to do it. The same can be said with Hand Signs. You might have seen a hand sign and memorized it, but you would have to practice how to make the Hand Sign or else it might not turn out right. Your hands might hurt from the strain as well since they aren't used to the positioning. It's like looking at Hand Signs on this very wiki. You see them, you know how they are done, but you might not be able to make them perfectly.

If you state no to any of the questions above, then your answer is simply, Sharingan cannot copy any jutsu then.