Nobody can guarantee that the package in the repository will be a fixed version.
It is possible to hold an installed package from upgrading, but
apt will always install an available version from the repos. Nobody keeps old versions there.
There actually may be two versions the initial one and an "upgrade" one.
But it is very unlikely that a package will be upgraded to some new major version in an LTS repository. Some minor fix may be released, but I don't think it can affect functionality.
sudo apt-get install tofrodos:i386=version
is the correct command. But there is no
1.17.3 version in the repos.
The correct version is
pilot6@Pilot6:~$apt-cache policy tofrodos
500 http://ru.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
sudo apt-get install tofrodos:i386=1.7.13+ds-2ubuntu1
It is the "initial" version for
xenial. Even if the package is upgraded in
xenial-updates the command will install this version.