If Cent & Turion apply Slow on themselves for 1 turn and then use their ability 3, they won't get Oink.

If they got Oink then using ability 2 both effects  apply to them (with Oink and without Oink).

If Cent & Turion apply ability 3, and then ability 2, the buff is not updated, but the buff icon is displayed above the hero and doesn't disappear. If they reuse any skills mentioned above, the debuff icon begins to stack (Repeated at levels 1 and 2, until there is a condition for shifting debuffs)

These are known issues, and we are already working on a fix!