Can he make a rock so big he can't lift it?
You quoted an answer to your question.
Making stone so heavy he could not lift it again goes against his omnibenevolent nature because by doing so God would limit his omnipotence, but omnibenevolence means love toward itself therefore God is not willing to limit it self.
This doesn't mean God is unable to do so, God certainly could do it.
A question with same weight would be, "Can God kill him self?"
Yes he could since it's omnipotent but it would not because it's also omnibenevolent.
This doesn't mean God is unable to do so, God certainly could do it.
Similar allegory:
I could kill my self but I will not do it because I love my self.
But this doesn't mean I cannot kill myself, I could and I hold that power.
Therefore God could make it (since it's omnipotent) but is not willing because he is omnibenevolent.
Similarly God can't make things which are logically impossible such as making 1 + 1 = 3 or drawing a squared circle.