RE: [CONNECT C++] How is Bentley::DgnPlatform::XDataTreeNode::GetECInstanceBySchemaName() parameter specified

It wants the "full" schema name, which includes the version numbers. i.e.: "MySchema.01.00".
The version numbers for item type schemas are always 01.00.
FYI...the XDataTree/ElementTempate APIs are largely undocumented and rather confusing.