Hey TPAKC-
In the second video of your comment, it appears you did not actually compile the changes after deleting the contents of the file. If you open the solution you should be able to right click on the project name and select the Build option to compile everything. The editor should be able to open after this. If this compile fails, please provide the output errors for additional info. Additionally, if you right click on the .uproject file you should have an option to “Switch Unreal Engine version”. You should be able to select this and manually switch the engine version from 4.14 to 4.15.
Cheers