Given the last part — in ROT13: kanwn → xnaja — maybe it’s "kanwn" intended as “kanown” (could be “known” misspelled) — so perhaps the original encoding is reversing words:
Atbash (A=Z, B=Y, etc.): t → g h → s m → n y → b l → o → gsnbo (no)
Given “g2410” is the key, maybe it’s a (G=4th letter, shift 24 = shift -2): thmyl tryf tabt kanwn g2410
But maybe each word is a scrambled anagram: — could be “mythl” or “thlym”? Unlikely.
Given the constraints, my best guess is: It’s a puzzle where “g2410” indicates ; “kanwn” could be “known” (if ciphered), and “tabt” maybe “that”. Given the last part — in ROT13: kanwn
“kanwn” might be “known” (k->k, a->n? no). But try reversing each word:
Not meaningful.
If shift -2: t → r h → f m → k y → w l → j → “rfkwj” — no.