It is incredibly unlikely that it was changes, this is a file server, and the changes were between the active full on the Friday night, and the incremental on the Saturday night. The business was closed during this time, so there should have been no changes. If you look at the previous weeks, before the upgrade to v9, the full was much larger, about 300gb, but the following day incremental was only around 10gb
To answer your other questions, it is only for this server, but this server is the only one with 2012r2 deduplication enabled.
No There were no operations performed between the 2 jobs