According to the i.MX6 ULL Application Processor Data Sheet (chapter Ordering information) there are several variants of this processor available. Those could be identified by a part differentiator.
So my question, is there some kind of register to identify those variants via software?
you didn't get my intension. For example i want to write a production program which identifies the capabilities of the running processor. I guess these information are hidden in the OTP register.