If the project was created in Creator4.0 ,then in backup folder there can be project which can be opened in previous version.
Otherwise there is no option to open a project created in Creator4.1 in Creator4.0
For some reason, even that does not work, once 4.1 has modified the project. It appears that the new data format is unreadable by older versions of PSOC Creator. It is a one way street.
I was able to copy and paste my way into 4.0 project. One request: make a schematic page fully copy and paste-able.