Unfortunately here on the Boards, we are only players (even I am just a volunteer player) so we cannot provide much assistance except advice. This really needs to be handled by Riot Support, but it sounds like you are having difficulty logging in to get a hold of them.
If you think your computer has been compromised by a hacker, before doing anything, scan your computer thoroughly using a good antivirus scanner. This will remove any viruses, malware, or other programs that may have allowed a hacker to access your account.
My first suggestion is attempting to recover your account -- https://support.riotgames.com/hc/en-us/articles/360037644973 -- by following this link and answering the questions. You shouldn't need to log in for that because it is meant for people who have lost access to their accounts by having their passwords hacked.
You can also read up on the recovery process here -- https://support.riotgames.com/hc/en-us/articles/201751694-Recovering-Your-Account
Best of luck! Let me know if you are still having trouble and I'll see what other ideas I can brainstorm.
[poppy-wink]