1: Is there any way HP Dataprotector can take diff. or incr. of the VHD file (virtual machine) like an incremental forever ?
If it were a Filesystem backup, you could could use Advanced Incremental (after doing at least one full Backup), and, periodically combine a number of Incrementals into a Synthetic full. I checked the Hyper-V documentation, and found nothing that indicates that this is an option
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2: And is there any possibillities with Data Protector now or will be in the future to Restore single files from a VHD backup without restoreing the whole machine and the mount the VHD file ?
There is functionality for VMware Granular Recovery EXtension, but thsi is only for VMware. We had a training class this morning where your question was asked, there are no plans at the current time to implement GRE for Hyper-V, and, I seem to recall that thsi is a Windows limitation
You can always request an Enhancement for Data Protector from this site: