Ahh, while I slept you guys managed to make such a mess

Giving hints for wrong numbers and everything.
2 - The name of the missing symbol, if it were used in mathematics.
3 - Count the letters to each word carefully and find the... irrational... pattern.
4 - a place that is literally "without tin".
5 - 1 has 1, 2 has 2, only one word in the dictionary has 3 of these.
6 - No idea how to get to 7, but warp to 9 with searching the title. It's an anagram.
7 -
8 - just adding this to avoid confusion.
9 - The vowel you want doesn't appear in any of the numbers.
10 - The honda "palindrome" is a model of car.
11 - The title basically tells you where the answer is. Ignore everything else. You might have already warped by doing this earlier.
12 - Easy - name the mahjong hand. Made me think of a Jonny Depp movie with a book with some link to the devil or whatever.
13 - The number 13 is missing because they're afraud of it. The title is scared, and they look scared. Look into the fear of the number.
14 - If you can't see that the answer is tne then go to bed

Ten Nine Eight S S F F T T O
15 - This one has pretty much been covered. Pay attention to the title, and don't ignore the fonts.
16 - Rearrange in MS Paint or whatever to get the name of the next level.
17 - The answer is the name of a game. I say... do the maze.
18 - Follow the instructions. Use morse code.
19 - Look to the source again, decode, then work out what to do next.
20 -
This is where I'm stuck and I need help :-D