3.1) Can I have two versions of a package in the same distribution?
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Sorry, this is not possible right now, as reprepro heavily optimizes
at only having one version of a package in a suite-type-component-architecture
quadruple.
You can have different versions in different architectures and/or components
within the same suite. (Even different versions of a architecture all package
in different architectures of the same suite). But within the same
architecture and the same component of a distribution it is not possible.

apt-get install packagename=version

dpkg-deb --info package.deb

md5sum package.deb