Vide the sample ROUND 4 ( Octopus Link ) in the instruction booklet for SM . I see no digit in same place in all 6 solved sudokus in BOX 1 ! Have i not understood the rules!

Look at the 6x6 grids for the linking logic. R1C3 is same. 9x9 grids do not have the linking logic.

What is slot machine sudoku ? And can you please give any tip on how to solve octopus link ?

Slot Machine:

The order of numbers in three columns (2,5,8) is the same. Consider row 1 as a continuation of row 9 for this purpose.

Look at the IB example
Col 2: 385279641
Col 5: 138527964
Col 8: 279641385

The starting numbers are different. But the order is maintained e.g. 9 always comes after 7 and is followed by 6.

Octopus Link

Try to find at least one common digit in each row, each column and each box by using all 8 grids. Whenever you find such a number, fill it in all grids. Once you are done with this step, solve each of the grids.

I'm still confused about the octopus link and skyscraper sudokus. can you please guide me with maybe first few steps of the examples?
I'm not able to get the right approach to get started :(

Skyscraper: Focus on column 9. There is a 7 clue at the bottom. So R9C9 can take values 1,2 or 3. If it takes any other value you cannot see seven buildings from that direction. Similarly R2C9 and R5C9 can also have 1,2 or 3. So we get a triplet in Column 9. The other cells must have the numbers from 4 to 9 and there is only one way you can place them to satisfy the 7 clue for the column.

Octopus link: The four 6x6 sudokus contain the linked example . Solve the inequality. You can solve it independently. Now look at column 1 for a common digit across all 4 sudokus. You should be able to eliminate everything except the 5 in r5c1.