First, you will need to add PHP repository to your server to install multiple versions of PHP. You can add Ondrej PHP repository with the following command:
apt-get install software-properties-common -y add-apt-repository ppa:ondrej/php
Next, update the repository with the following command:
apt-get update -y
Once the repository is up to date, install PHP 7.0, PHP 7.2 and PHP-FPM with the following command:
apt-get install php7.0 php7.0-fpm php7.2 php7.2-fpm -y apt-get install php7.4 php7.4-fpm php7.4 php7.4-fpm -y