If you player’s level is above the limit for the applicable content, the following pe

"If you player’s level is above the limit for the applicable content, the following pets they are in control of will no longer despawn upon starting"

In English, please. Not sure what this is say, but I will give it a try with three examples.
Does it mean:

If the player's iLevel is 119 and they begin a Level 119 unity battle the pet will disappear because the player is not above 119.

But if the player's iLevel is 119 and they being a Level 99 unity battle the pet will not disappear.

If the player's iLevel is 119 and they begin a Level 126 unity battle the pet will disappear because the player's iLevel is not above 126.

Is this what you mean?