The golden age is all fine and dandy, but the alternative has negative infinity payoff, so your only rational choice, unless you can discover with certainty before answering whether the alien is a liar, is definitely option 3.
Outcome: your dinner has similar nutritional content to your customary astronaut nutrient slurry, but it tastes better.
Plot twist: the alien meat tastes like vanilla ice cream, only much better. You suddenly understand the reason behind the question. You feel an overwhelming urge to find and eat more aliens.
Substitute an alien with different responses and you get a different set of outcomes. What's the point?
Option 3 would probably end up with the astronauts getting a bad case of diarrhea if not worse, since the alien would probably be made of something different than the basic building blocks of earth biology. So outcome 3 should be more like:
Outcome: your dinner has an interesting taste, after which you all die of arsenic poisoning. Zero lessons have been learned - you really should have paid more attention during your exobiology classes.
You are an astronaut on an expedition to Mars when you encounter an Alien. Luckily, it speaks English, and you begin an exchange of cultures: history, art, technology, and food, whereupon the Alien interrupts:
“Our species has strong feelings about ice cream flavors. Tell me, what is your favorite flavor? If you answer chocolate, all is well, and our races can coexist. If you answer vanilla, we will annihilate every human.”
This is a dilemma, for you strongly prefer vanilla ice cream, but you have preferences against both lying and having humanity annihilated. You consider your moral framework.
“I like chocolate ice cream,” you lie. One tiny moral lapse is worth saving all humanity.
“Aha! Liar!” screams the Alien. “The question was a test, for we have mind-reading technology. How do you think I learned English so quickly? In retribution for your treachery, we shall destroy all humans, starting with you.”
Outcome: Humanity annihilated.
“I like vanilla ice cream,” you answer truthfully. You would never compromise your moral principles. Also, you aren’t convinced these Aliens could defeat your nukes.
“Very brave of you,” says the Alien. “What our species truly values is integrity. As a reward, I gift you this machine, which provides limitless energy, faster-than-light travel, immortality, and a few other things…”
Outcome: Humanity enters a trillion-year golden age.
“I like…” you begin, then draw your phaser pistol and shoot the Alien in the face.
The Alien collapses, dead. You stand over its smoking corpse, not feeling any remorse, for you don’t think non-human species carry moral weight, and you are pleased at finding a way out of your ethical dilemma.
You wait to see if other Aliens might spring from behind the rocks, or if you are atomized by an orbital laser. Nothing happens.
Eventually, you decide there’s no point in wasting good protein, and you’re not vegetarian. You haul the Alien back to base, announce “Looks like meat’s back on the menu, boys!” to your fellow astronauts, and cook the Alien for dinner.
Outcome: your dinner has similar nutritional content to your customary astronaut nutrient slurry, but it tastes better. Zero lessons have been learned.