To quickly answer your questions:
A: There is an XSD schema, but only to ensure if the document is a valid CDA document (this means it only validates the CDA RIM, not the CCD Implementation Guide)
B: The non-schema based method is to use schematron, and a ccd.sch does come shipped with the standard provided by HL7. This is the best way to validate it as a valid CCD document.
C: There is no such thing as a ccd.xsd that I'm aware of.
Background
Here's a bit of background and instructions on how to acquire the CCD standard from HL7. Acquiring the Standard would also provide you with the CDA.xsd and CCD.sch for file validation.
CCD is a specific implementation derived from the CDA RIM. Both CCD and CDA are standards that are maintained by HL7. CCD is currently a “Section 1” type standard by HL7.
The full standard can be downloaded from the HL7 website. The full standard is full standard is free to download - Although you may have to register to the site (also free). http://www.hl7.org/implement/standards/product_brief.cfm?product_id=6
Because I don’t know what other resources you have available, I am going to only use supporting documents that can be acquired from the HL7 website.
There are two layers when it comes to validating a CCD document. First, you have to validate to make sure that the document is a valid CDA file, and then you have to validate to ensure it follows the implementation constraints outlined in the CCD Implementation Guide.
To make sure it is a valid CDA file, there is a CDA.xsd schema that comes with the full CCD spec download.
The standard also comes with a schematron file to validate it as a CCD document.
In the unlikely scenario that there is a disagreement between the schematron validator and the Implementation Guide, always go with the Implementation Guide.
Acronyms
CCD – Continuity of Care Document
CDA – Clinical Document Architecture
RIM – Reference Information Model
As a supplementary link, a pretty handy online tool for CCD document validation can be found here: https://www.lantanagroup.com/validator/