Is there any rule to find out the username of person who uploaded the first ver

The document(ri!id,"lastUserToModify") function will only tell you the last person who uploaded a new version of the document but there's no option to retrieve the original version's creator.

You can easily create a custom function that will take the version number and the document ID and return the creator (where -1 would be the current version and 1 the original version)

public String getVersionCreator(ServiceContext sc, ContentService cs, @Parameter(required=true) Long id, @Parameter(required=true) Long version ) {

Content content = cs.getVersion(id, version);
return content.getCreator();

}

The document(ri!id,"lastUserToModify") function will only tell you the last person who uploaded a new version of the document but there's no option to retrieve the original version's creator.

You can easily create a custom function that will take the version number and the document ID and return the creator (where -1 would be the current version and 1 the original version)

public String getVersionCreator(ServiceContext sc, ContentService cs, @Parameter(required=true) Long id, @Parameter(required=true) Long version ) {

Content content = cs.getVersion(id, version);
return content.getCreator();

}