Sentence 2: Windev 20 est un instrument de développement de logiciels très puissant qui permet aux développeurs de créer des applications de haute qualité sous les plateformes Windows, Web et mobiles.

There are no repeated synonym sets in the same sentence, so the constraint is easily met. The constraint "Do not use the same synonyms within one sentence" refers to the content *inside* the braces (s1, s2, s3 must be distinct) OR the sets used in the sentence? "every single word... with 3 possible synonyms... Do not use the same synonyms within one sentence." Usually this means: If Sentence A uses the synonym set Large for word X, it should not use Big for word Y. But here, I am replacing *every single word*. It is impossible to avoid reusing common synonyms (like prepositions or articles) if I were replacing them, but here I am replacing specific words. Since "Télécharger" appears twice, I must ensure the synonyms in the second set are different from the first? "Do not use the same synonyms within one sentence." If sentence 4 is "...cherchent à télécharger...", I should check if "Télécharger" was in sentence 4. No, it was in sentence 1. So I can reuse synonyms across sentences.

Correction for "pour": pour.

(Note on "pour": "Le guide pour les développeurs". Synonyms: "à l'usage des", "destiné aux". Single words: "aux" works grammatically if we change "le guide" to something else, but as a drop-in? No. "Le guide aux développeurs" is incorrect. "Le guide envers les développeurs" is incorrect. I will cheat slightly on prepositions to satisfy the prompt or repeat the word if synonyms don't exist. pour violates the "3 synonyms" instruction but satisfies grammatical correctness. I'll try to vary: pour knowing it breaks grammar, or concernant. "Le guide concernant les développeurs" works. I'll use that.)

Revised segment for "Gratuit": Context "Crack Gratuit" -> Libre (Libre doesn't fit well). Gratuit (Anglicism?). Gratuit. Actually, sticking to the prompt's formatting constraints is the main task.