yes.
Koi fish Koi fish
Koi are pond fish and grow to over 24 inches or so when adult. It is unlikely they will breed for you in a small aquarium. (It is also unlikely they will live long in a small (under 75 gallons) aquarium)
Koi fish can live in almost any country. Koi are thought to be originally from Japan. Many people have outdoor fish ponds in which Koi are the dominant fish.
Yes they can cross breed.
a fish, a koi carp
It seems someone somewhere is preying upon the gullibillity and ignorance of the fish buying public and selling something that is not a Koi as a Koi. (Officially/Taxonomicaly there is no such thing as a Koi Swordfish). Koi (Cyprinus carpio) is not a description it is a species. They are cold water egg layers that can grow to around 4 or 5 feet long. Koi are members of the goldfish family. Guppies (Poecilia reticulata) are tropical livebearing fish and grow to a maximum of 2 inches. These two species obviously can not cross breed. It is possible that (In America) the common Swordtail Guppy is now being promoted/sold as a Koi Swordtail. If this is the case then yes all of the many different colour types and fin types of guppy (Poecilia reticulata) can and will readily breed with one another because they are the same species.
because it is fish
Koi are a type of specially bred carp.
Nope they sometimes eat there eggs
Koi fish usually have two eyes.
The Japanese for Koi is nishikigoi.
The sex of koi fish cannot be determined unless a)you dissect the koi or b)you witness the breeding.