Firefox is opening twice instead of once, usually the "wrong" one opens

A few questions: What operating system are you on? Can you describe how Firefox is being launched? Is this happening when you open it from the taskbar/dock, start menu/spotlight search, or something else? Or happening when you boot your computer perhaps? When you say "the version with the preset tabs" and "the version you don't want"... are you talking about actual Firefox version numbers (like 157 or 158)? If not, what is the difference between them that makes you know "this is the right version and this is the wrong one"?