read this over and see if you've tried it before. the 0.75 and 0.74 numbers will be different in your folder, those are older patches but
go into the league_client folder (Riot Game> League of Legends > RADS > Projects > league_client > releases) i saw that there is 2 folders 0.0.0.74 and 0.0.0.75 i assume the issue is when u launch the client it runs the league client inside 0.0.0.74 >deploy folder which is an older version.
in this case and when i ran the league client in 0.0.0.75 > deploy folder ( Riot Games\League of Legends\RADS\projects\league_client\releases\0.0.0.75\deploy\LeagueClient.exe ) it scans some files (takes few min) then no restored to older installation message appeared you good
This might be totally irrelevant, not sure lul