How do I open multiple projects/folders in a single Visual Studio Code instance, and open multiple files in single view? Does it has any option for future change request?
As mentioned in several other answers here, this 'accepted' answer is outdated and is no longer correct. VS Code now has the concept of a 'workspace' which lets you add several 'root' folders to VS Code in the same window.
For instance, when working on a project in one folder that utilizes shared code held in a different folder, you can now open both the project folder and the shared folder in the same window.
To do this you use the Add folder to Workspace... command. VS Code then saves this configuration in a new file with a .code-workspace extension. If you double-click that file, VS Code will re-open with both folders present.
As described in The Basics of Visual Studio Code article:
"VSCode is file and folder based - you can get started immediately by opening a file or folder in VSCode."
This means the concept of solution and project files, like the .sln and .csproj, have no real function in VSCode other than that it uses these only to target and identify which language to support for Intellisense and such.
Simply put, the folder you open is the root you work with. But of course there is nothing from stopping you to open multiple windows.
As for the request features options, navigate to Help > Request Features which will redirect you to the UserVoice page of VSCode.