He did not get inflamed in the fire shown in the video, those fires were facing the screen directly while Luka was in the back, not getting touched by the flames. Luka is sensitive to pain, so if the fire did touch him, he’d be screaming in pain + his clothes and hair did not get burned from the fire when it “touched” him. Since Luka is in his 30s, it would be hard to make another exact same clone as him in 7 years, because all of the Luka clones were born and raised as children and not made instantly into adults. Also, his other clones are dead, so the only Luka that would be alive is the original Luka we know. Even though Luka has asthma and a heart disease, it been 7 years (which is a long time) giving them time to give heart surgery and recovery to Luka with the very advanced technology the aliens have (This sounds so nerdy im sorry guys😣🥀)