To use the chain strategy, pick a box with only 2 candidates that you would like to solve. Now imagine that the answer to that box is the first candidate. Then add the effects of changing that box, and you will find yourself with a chain of numbers. Now think that the box is the other candidate. In most cases, a box or too in the chain will be the same number in both variations. You can now deduct that that square is solved.
Multi Sudoku is one of the challenging but at the same time, interesting sudoku variants that have been developed in the logical world of puzzles. It is a sudoku puzzle that consists of two or more sudoku grids. The unique part of multi sudoku is that certain region(s) of the sudoku grids are overlapping each