No, anyone can make sudokus.
Yes, of course Sudoku is copywritten. If it wasn't then people could go and steal it. If you don't believe me, you can go to Google and look it up. ( yes, Google is copywritten too!)
There are 2025 rectangles in a 9x9 grid.
Sudoku
81 squares on a sudoku grid
The game you are thinking about it Sudoku http://en.wikipedia.org/wiki/Sudoku The game you are thinking about it Sudoku http://en.wikipedia.org/wiki/Sudoku
There are 9 rows and 9 columns. There is 81 individual squares in one grid.
I am assuming you are referring to a normal 3x3 sudoku grid, where you can only use the numbers 1-9 once in the grid, and by prime number you mean the 3digit number across and down the grid must be prime? For a number to be prime, it must end in 1, 3, 7 or 9. There are 5 places on the Sudoku grid for a number to finish and as you can only use a number once in sudoku you have one place left where the number can not be prime. This means the most you can have is 5 prime numbers.
Kakoru or kakuru is a cross between sudoku and crossnumbers puzzles. There's also "killer sudoku" which is just a larger grid size (12x12 or 16x16.)
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The mechanics involved in sudoku follow the principal, that any 3x3 grid can be filled with the numbers 1-9, every row can have 1-9, and every column can have 1-9, to eventually have a complete 9x9 grid filled with the numbers 1-9, where no numbers in any row, column, or 3x3 grid have two of the same number
Twilight was copywritten in 2005 by Stephanie Meyer.
These games are generally referred to as "logic puzzles;" however, this can also refer to any kind of puzzle where one finds the solution through logic (picross, sudoku, etc.), but the ones you refer to are still referred to as "logic puzzle" alone. Thank you! I found a great website. http://www.puzzlersparadise.com/page1042.html