An eyeball is a round organ that allows an organism to discern the different frequencies of light emitted by its surroundings. In simple terms, it lets an animal know what is around it by reacting to...
your eyes.
Squishies can be bought in vending machines at many major malls, restaurants and drug stores. They can also be bought online.
If you don't mind being blind in that eye.
No, an infant's eyeball is about 65 to 75% the size of a grown person's eyeball. They do get bigger, mostly before puberty.