Hello,
I do not know the answer to your first question, however, you could clone 
tape A & B to C and discard A & B through cloning operation, not sure if 
that is feasable in your enviroment where you may have to send tapes 
offsite at certain time.
As a matter of fact you could just clone all your tapes ( time permiting) 
to make a better use of your tape capacity, another approch would be to 
write to Adv File Type of device and clone or VTL and or DISK backup and 
clone.
HTH

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