1) In Modern French, the grapheme “oi” is pronounced as the diphthong /wa/, and the grapheme “oy” does not exist. However, both would have been pronounced as /oj/ in Old French.
2) The graphemes “s” and “c (+ i, e)” are pronounced as the voiceless lingua-alveolar fricative /s/ in Modern French, but they would have been pronounced as the voiced alveolar affricate /ts/ in Old French.
3) In Modern French, the word-final “e” is not pronounced, but in Old French, it would have been pronounced as the mid center schwa /ə/.
4) In Modern French, “g (+ e,i)” and “j (+ a, o, u)” are pronounced as the voiced lingua-palatal fricative /ʒ/. In Old French, however, this palatalization was not yet complete, so those graphemes would have been pronounced as the voiced alveolar affricate /dʒ/.
5) Although the grapheme “au” is pronounced as the mid high back /o/ in Modern French, it was still pronounced as the diphthong /aw/ in Old French.
6) Similarly, the grapheme “ou” is pronounced as the high back /u/ in Modern French but the diphthong /ou/ in Old French.
7) In Modern French, the grapheme “ch” is pronounced as the voiceless lingua-palatal fricative /ʃ/, but it would have been pronounced as the voiceless lingua-alveolar affricate /tʃ/ in Old French.