Debian apt-get downgrade

Exemple 1

apt-get clean apt-get update apt-cache policy perl-base apt-cache show perl-base |grep ^Version apt-get install --reinstall --allow-downgrades perl-base=5.24.1-3+deb9u4 #apt-show-versions -i #apt-get install $(apt-show-versions | grep -P 'newer than version in archive' | awk -F: '{print $1"/jessie"}') #apt-get install -V $(apt-show-versions | grep -F 'newer than version in archive' | awk -F: '{print $1"/'$(lsb_release -cs)'"}')

Exemple 2

# apt-get install install libopencv-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package install
root@BGX-deb98:/home/process# apt-get install libopencv-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
libopencv-dev : Depends: libopencv-objdetect-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libopencv-highgui-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libopencv-legacy-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libopencv-contrib-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libopencv-videostab-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libopencv-superres-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libopencv-ocl-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libcv-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libhighgui-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
Depends: libcvaux-dev (= 2.4.9.1+dfsg1-2) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

# aptitude install libopencv-dev
...
The following packages have unmet dependencies:
libglib2.0-bin : Depends: libglib2.0-0 (= 2.50.3-2) but 2.50.3-2+deb9u2 is installed
libglib2.0-dev : Depends: libglib2.0-0 (= 2.50.3-2) but 2.50.3-2+deb9u2 is installed
libicu-dev : Depends: libicu57 (= 57.1-6+deb9u2) but 57.1-6+deb9u4 is installed
...

apt-get install --allow-downgrades libglib2.0-0=2.50.3-2 libicu57=57.1-6+deb9u2