The p and f sounds are both the same Hebrew letter pe (פ), with or without a dagesh, a dot in the middle of the letter denoting the “hard” (p) sound. The pronunciation changes depending on the phonetic context: it’s pronounced hard (p, written with dagesh) at the beginning of a word or when following a consonant, soft (f, written without dagesh) when following a vowel. The pronunciation rules are different in Arabic.

I have no idea what you mean about “God’s instruction” and “Satan’s pride,” or what they have to do with the Hebrew letter.