Irregular usted and ustedes command forms
My book say that these are the verbs and their irregular Ud. and Uds command forms
On the conjugemos site irse is given as
positive: vete negative: no te vayas...
Does this make sense?
There is a chart, if you scroll down to the bottom of the page, of irregular command forms.
Those forms in your book with the irregular Ud. and Uds command forms are only polite forms.
The formal imperative of dar is regular, but "dé" is written with an accent to differentiate it from the preposition "de".
With "estar" the irregularity is the change in the position of the stress only.
"ir" and "saber" are rather irregular.
The regular imperative of "ser" would have been "sa" and "san", so that is also an irregularity.
The forms "vete" and "no te vayas" are informal, unlike all the previous examples.