What is the max number of words one can construct using this combination of letters?There are 325 words possible using words that start with 'os' and include 'a'.
What's the longest word you can make using this list?'osteochondrofibroma' (19 characters)
Which word from this page is the most unusual?The most stand out word from this page is surely 'oscitantly'. According to the Oxford dictionary, 'oscitantly' is defined as "In an oscitant manner.".
What is the most popular word that starts with 'os' and includes 'a'?A common word for your request is 'ostentation'.
What's the highest scoring word in Scrabble available from this list ?Since there are a massive 325 entries, your best option is to consider 'osmazome' which scores 21 points.