iridophobiai belive it is called
There is no official phobia name for the fear of vipers. However the official phobia name for the fear of snakes is ophidiophobia.
rainbows
Iridophobia is the fear of rainbows.
There is no official phobia name for fear of the alphabet.
There's no official name for the fear of hot dogs.
It doesn't have an official name, but loving cheese is Tyrosemiophilia, so I'd assume the fear of cheese is Tyrosemiophobia.
There is no official name, though cerasumophobia may be informally used.
An opossum is a type of marsupial mostly found in the Western Hemisphere. There is no official name for a fear of opossums.
Someone said Acrophobia which is a lie, Acrophobia is actually the fear of heights, this is because acrobats are up in the air all the time up high. The answer to your question most likely will not be official, the name for the fear of clowns (coulrophobia) is still not the official name but instead the name most people just call it.
Pocketful of rainbows
It has been casually referred to as "Castle-a-phobia", but there is no official name for this phobia.
The scientific processes that forms rainbows is called refraction and then reflection. Rainbows themselves do not have a specific scientific name.