It's possible to run System Restore using a repair DVD, but you have to have one first.
A repair shop will have one.
You boot off the repair DVD (or Windows 7 DVD) and get a menu like the one shown at the bottom of this pagehttps://www.pcworld.com/article/252927/restore_your_system_when_you_cant_launch_system_restore.html
Since you'd be using the OS on the repair DVD it wouldn't matter that file associations are messed up in Windows on the hard drive and you'd be able to left-click as usual.
We're assuming the only problem is messed up file associations and not a hardware problem or some other problem that wouldn't be fixed by system restore. Whatever it is, the repair shop should be able to fix it.
Here's how Google says to download a file in Chrome
What they tell you to do in Step 5 -- and that you should NOT
do) is "When the download finishes, you'll see it at the bottom of your Chrome window. Click the file name to open it." NOOOO!!!!!!!
You don't want to open a save file using Chrome and I don't know why they tell people to do that without knowing what kind of file was downloaded.
Chrome and Windows won't know what to do with a save file, and if the user clicks something in desperation they may end up creating a bad file association. Saves should only be opened by the game that made them -- by putting the save in the save folder, starting the game, and loading the save from the game's menu.