Just as humans differ in their understanding and natures, so too do animals. This is illustrated by what was recounted regarding the ant of Solomon—Exalted is His Might. The Almighty said:
{An ant said, "O ants, enter your dwellings that you not be crushed by Solomon and his soldiers while they perceive not."} 1
And the Almighty said regarding the hoopoe:
{But the hoopoe stayed not long and said, "I have encompassed [in knowledge] that which you have not encompassed, and I have come to you from Sheba with certain news. Indeed, I found [there] a woman ruling them, and she has been given of all things, and she has a great throne. I found her and her people prostrating to the sun instead of Allah, and Satan has made their deeds pleasing to them and averted them from [His] way, so they are not guided."} 2
As for the third question, its answer remains unknown, concealed behind a veil. The Divine portal has not addressed this matter directly; however, we might say, by way of deduction, that the most intelligent creature from every nation of animals could potentially be its messenger.