1. This may be the first prayer Catholic children learn:
"In the name of the Father, and of the Son, and of the Holy Spirit. Amen."
How is this short prayer called?
From Quiz Catholic Prayers for Young People
Answer:
The Sign of the Cross
The Sign of the Cross can be made before a prayer, after a prayer, or as a prayer by itself. The "Sign of the Cross" can refer to the prayer itself or to the gestures made when reciting the prayer. A Catholic makes the Sign of the Cross with the right hand, touching the forehead at "Father", the heart at "Son", and each shoulder with the "Holy Spirit". And so this prayer invokes all three Persons of the Holy Trinity.
When my father was an altar boy in the 1940s-50s, he learned the Latin version: "In nomine patri, et fili, et spiritu sancti. Amen." Nowadays, most Catholics use the vernacular, which means the language they normally speak to each other. Some in my father's generation and earlier also called the Third Person of the Trinity "Holy Ghost", but "Holy Spirit" is most common in the USA now.