For words that have only 3 letters, there is no 4th letter. For example with the word “insert”, there aren't any more letters afterwards and thus need to be the word "include". The word “addict” is during the BIP39 wordlist however you would've utilised “addi” for “addict”. Standard recovery phrases https://bookmarkshut.com/story19679169/the-2-minute-rule-for-bip39-all-words