"On His Having Arrived at the Age of Twenty-three" is a Petrarchan sonnet, which consists of fourteen lines and a specific rhyme scheme. This type of sonnet is traditionally divided into two parts: an octave followed by a sestet.

The poem with the first line "At age 3" is from the collection "Milk and Honey" by Rupi Kaur. You can find it in the section titled "the hurting."

At least two, but it depends more on the kind of poem you're writing. Some have three while others have twenty.

...and some can have a hundred and twenty!

twenty three and a half

23 and 1/2

11.875