They do. They are installed in different locations. Windows Powershell : “C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe” and Powershell Core (or 6.2 or 7.0rc1 or what ever): “C:\Program Files\PowerShell\7-preview\pwsh.exe”
Of course. You simply choose the version you need by the executable you start.