awk '
                        {(gsub(/ +/," "))}         ##### gsub is used for substitute operation, like here we are replacing the spaces which are unequal to a single spaces, like in row number 2 you have showed us in input space is NOt a single space. So that we can make equal length in between fields of each line.
!T[toupper($0)]++                                  ##### toupper is a utility by which we can covert any string/line to completly capital form. Here we are creating an array named T whose index is the complete line which  has been changed toupper cases now, !T[toupper($0)]++ means if the line haven't occur even a single time than make that specfici line's count as 1 and ! sign before aray T makes sure no lines should have count more than 1, so that we can have unique single time lines only. As we know awk works on 
                                                         condition and action format, means if any condition is RUE then action mentioned next to it should be perfoemed, here when any lines comes first time into array T then it will print it too because we haven't given any action and default action in awk is to print.
' file                                             ##### mentioning input file name here