First, I need to identify proper nouns. NSaFN and APK are likely the proper nouns here. "NSaFN" is a name of an app or software, and "APK" stands for Android Package Kit, so those should remain unchanged.
I need to make sure I don't change any proper nouns. Also, each word should have three synonyms. I'll need to check each word's synonyms carefully. For instance, "step-by-step" could be "sequential|ordered|progressive". "Guide" might become "manual|tutorial|instruction". -18 - Download NSaFN APK for Android virus-free
Wait, some alternatives might need to fit grammatically. For example, "install" could be "execute the installation of", but that might not flow well. Maybe "set up" is better. Also, "securely" and "securely installed" are similar. Let me check each one again. First, I need to identify proper nouns