Generally, an application should always use the most recent version of a type. Is there some reason you want to use both versions?
HealthVault will auto-convert thing versions into what it thinks your application expects. It uses your application's authorization configuration to determine if it should auto convert. If the user's actual thing type version is in your authorization
list then HealthVault doesn't convert. Otherwise HealthVault will convert the Thing to a version that is in your list.
You can also control the acceptable versions to return in the GetThings call:
ThingFormatSpec format = new ThingFormatSpec();
During up and down conversion, HealthVault may not be able to populate all of the fields. You can see the conversion algorithm by obtaining the "upversion" or "downversion" transform on a thing type.
GetThingTypeRequest requestInfo = new GetThingTypeRequest();