Is it safe to move Windows C:/ partition?
Both UEFI itself and the Windows Boot Manager find the next partition by reading the GPT partition table; the boot process does not rely on the file or partition locations being fixed.
(The Windows Boot Manager does however expect the partition numbers to remain the same, so while moving and resizing partitions is safe, adding/deleting/swapping can cause problems unless it's done through Windows DiskMgmt.)
As far as I know, the "MSR" partition doesn't really do anything.