Oh, sorry for being late, i missed the original message. Your request - to me - sounds like a contradiction: IoT lets me assume, you want to have some network connection wheras Jessie would want you to avoid any network due to it being totally out of time and thus has no chance to sync with anything (updates/security/and so on)
If you absolutely need the latter, you would have to set such an internal repository-server up for yourself, or at the very least stop apt from doing its job. The easier path would be to have a VM that never reaches the outside world (which would happen, if you do not inhibit it), by using VirtualBox to have an internal net instead of the NAT/bridged setup. This way, you could even time-shift the VM in question and move it into the past, but never reach the outside world with its clocks and software. Your job to find out, what you really want/need and to act accordingly. Maybe the assignment was outdated in the first place? Maybe the teacher wants you to solve some of the problems, that arise automatically, if you naively follow practices from years ago? Just my 2 cents DdB
