Yes! They are a kind of horse.
There is no collective noun specifically for stallions, however there are a number of collective nouns for horses that would be suitable, for example:a herd of stallionsa stable of stallionsa field of stallionsa stud of stallions (breeding animals)a string of stallions (breeding animals)a pair of stallionsa drove of stallionsa troop of stallions
Stallions is the plural.Stallion is the singular.
Like any other stallions do.
Boise Stallions ended in 2001.
Boise Stallions was created in 1999.
Dallas Stallions ended in 1999.
Dallas Stallions was created in 1999.
Baltimore Stallions ended in 1995.
Baltimore Stallions was created in 1994.
Birmingham Stallions was created in 1983.
Birmingham Stallions ended in 1985.
Augusta Stallions ended in 2002.