Here, freed from pain, secure from misery, lies
A child , the darling of his parents’ eyes:
A gentler lamb n’er sported on the plain,
A fairer flower will never bloom again:
Few were the days allotted to his breath;
Now let him sleep in peace his night of death.

The stylistic figure we see here is called alliteration, which consists of the first letter or sound of a word being repeated multiple times in close proximity, like we see here with 'freed from' and 'fairer flower'.
This is a run on lines, often used to emphazise the last and first words of a line. It is used here to stress that this is the tumbstone of a child.
Our next stylistic is called an 'Anaphora' which means that the first word of a line gets re-used as the first word of other lines. These sentences can also be seen as enumeration, a literary device where multiple of the same thing get noted (in this case qualities of the child)
This is a metaphor, here to represent the innocence of the child due to being represented as a lamb.
These lines are examples of a eufimism, a way to soften a harsh statement. In this case the harsh statement is the fact that the child had passed away