A sudoku with only four given digits and some more rules

Ok so this is one of the hardest sudokus (and one of the best sudoku) I have ever seen, with only $$4$$ given digits. There are some more rules too :-

$$(i)$$ First, normal sudoku rules apply here.

$$(ii)$$ Both the diagonals also should contain $$1$$ to $$9$$ in some order.

$$(iii)$$ You cannot put the same number in cells which are at a knight's move (in chess) apart.

$$(iv)$$ The center box will be a magic square.

Now comes the real part, can you solve it?

Bonus :- Is the solution unique, or can you find any other solutions?

Edit :- This is not a puzzle of my own devising. However, to avoid spoiling the solve for others I will wait to declare its source until the puzzle is solved. Credit goes to Mark Goodliffe and Simon Anthony for solving this puzzle, and also to Aad Van de Wetering for making such a wonderful puzzle !

Edit :- This puzzle got solved here :- https://www.youtube.com/watch?v=hAyZ9K2EBF0

• Don't forget to attribute where you found this so the original content creator gets credit! Thanks :) – Stiv Oct 9 '20 at 9:17
• Shall Do it after the puzzle gets solved, don't want to ruin the solution(which is already there) :) – Anonymous Oct 9 '20 at 9:28
• It's fine to put a message to that effect - see Rand's meta post to that effect. A holding line like "This is not a puzzle of my own devising - however, to avoid spoiling the solve for others I will wait to declare its source until the puzzle is solved." would be fine :) – Stiv Oct 9 '20 at 9:50
• I get it, will do it now. – Anonymous Oct 9 '20 at 10:12
• I've seen the video in which this is solved so I wont answer as I feel like it would be unfair, but agreed, this was a really clever puzzle! – Beastly Gerbil Oct 9 '20 at 15:08