hello, I was doing this sudoku and i decided to do something that I dont know if is allowed or the name of it.

ok so I had the number 5 highligthed so then I detected those 2 red lines, after that I assumed if the 5s were the ones in the corner and everything worked perfectly so i went ahead to see if the 5 in the middle of the red lines would work aswell and I was stuck because there were several possibilities, but then I looked at the blue block ok there are only 2 numbers for this and the first one that worked eliminated one of them so now i can imagine? maybe if that the 5 blue in the corner is the one that exists and combine those 2 possibilities to eliminate candidates, so it worked but was there any chance to #### up or is this actually a method?