how are beginners supposed to know that שישה can be written also ששה? stop giving us possibilities that haven't been tought before!
Take it as a rule of thumb that if they sometimes omit the letter "ו" and "י" then it is not a spelling mistake.
I was under the impression that this was related to gender up until this example where gender is the same for both forms, so it's definitely better to clarify explicitly :)
You don't. That's how you learn. Lucky for you, your grade doesn't affect you.
YES! :) We can all make mistakes and learn from them without penalty or embarrassment!!
Hope this will help: https://en.wikipedia.org/wiki/Ktiv_hasar_niqqud#Rules_for_spelling_without_niqqud