no
it is correct if you mean it as too many/a lot of shoes on the floor. any other way would be incorrect
Lo que usted dice es lo que dices y lo que haces es lo que haces
You can say 'says I' When you are arguing with somebody. Goes like this: "Who says I am made of gold?" "Says I!"
"Plethora" is a singular noun, so you say "is a plethora."
Plethora is singular and the plural form is plethoras