The English Bible itself is a translation. It didn't say John in the originals.
The name is ultimately derived from the Biblical Hebrew name יוחנן (pronounced [joχanan]), short for יהוחנן (pronounced [jehoχanan]), meaning "God was merciful".
It's dependent on the translation what they decide to use.
Yes. This is most correct but the map is made for English speakers where John is what is ubiquitously known and most people don't understand the biblical origins.