Hi I have a laptop of Windows 10 with 4gb ram I have already install office 2016 on it can I still install Office 2000 on it

Why? What is the driving requirement to do so?

Would expect that Office 2016 would be backwards compatible with older Office 2000 documents.

Both applications could be installed but I would be very wary of any conflicts or issues with updates etc..

Office 2000 might, for example, overwrite a newer component being used by Office 2016.

May not end well with both applications then having problems or conflicts.