We have two pieces of information (the other fragmentary bits are, I think, irrelevant): the key given as 70656c636762207a726e61662070656c636762207a726e, which interpreted as a string of ASCII characters is "pelcgb zrnaf pelcgb zrn", whose ROT13 is "crypto means crypto mea"; and the ciphertext given as 200000000000471f0411060a0c43061115541f520c061507104543131714541c541801184e1c0552111910064e0a450800154f111f18041d004e. And, as Bass points out in comments, there is a caret suggestive of XORing.
So, suppose we
begin by XORing the key we have with the first part of the ciphertext (note: the key is shorter than the ciphertext). We get "Cryptography, the pract". Looks promising.
It's rather obvious that
the key seems like it might be the first portion of a repeating cycle: "crypto means crypto means crypto means crypto mea...". If we XOR that byte-by-byte with the ciphertext, we get this: "Cryptography, the practice and study o%1c``r!*(ma{<1|j}mt!"
Clearly we're doing something right here, but clearly something's gone a little wrong. But
we have enough now to suspect that this might be a quotation. So put "cryptography the practice and study" into your favourite search engine. You'll find a few plausible continuations, but the one that jumps out as most likely ends "... of hiding information", which has the not-immediately-obvious merit of being the right length.
If that's the plaintext, what was the key?
Well, if plain = cipher XOR key then key = plain XOR cipher, and from this we find that the actual key was "crypto means crypto means crypto meanscrypto means crypto ". It seems that a space has been misplaced for some reason.
That's how I happened to find it, but
you might think googling likely answers isn't in the spirit of the thing, in which case I commend to you the following alternative approach. Our slightly-garbled plaintext gets as far as "Cryptography, the practice and study o" before descending into chaos, and it's natural to guess that the next plaintext character is an "f" and the one after that a space. This tells us that the key begins "crypto means crypto means crypto meanscr", and that's surely enough to make the same guess about a missing space.
Anyway, the plaintext is:
Cryptography, the practice and study of hiding information"
