Why is apt-get ignoring preferences?

Question

linux

Good time, the essence of the problem: there is Ubuntu 18.04, you need to install the package from the Ubuntu 16.04 repository, connected it to sources, I try to write in preferences:

Package:
Pin name: release n=bionic
Pin-Priority: -10
Package:
Pin name: release a=bionic
Pin-Priority: -10
Package:
Pin name: release n=xenial
Pin-Priority: 1001
Package:
Pin name: release a=xenial
Pin-Priority: 1001
Package:
Pin name: version version* (here the one in bionic)
Pin-Priority: -10
Package:
Pin name: version version* (here the one in xenial)
Pin-Priority: 1001

Not a single rule, pancake, plows, neither a=, nor n=, nor version, although, it would seem, just one with Pin-Priority greater than 1000 is enough for apt to even allow downgrade of the version from bionic to xenial, not to mention about installing "from scratch" immediately from this repository, while even the blacklisting of the version from bionic does not work, apt-cache policy shows the same priorities for all sources.
I don’t know what to do anymore, where to dig?