Web lists-archives.com

Optimizing use of /var/cache/apt/archives/ by Synaptic &/or apt-get

This actually two 'related' questions.

1. If /var/cache/apt/archives/ has the same or later version version of a package, will Synaptic and apt-get automatically use contents of /var/cache/apt/archives/ in preference to downloading whatever is at location specified by sources.list?

2. If there is no internet connection at the moment, will Synaptic and apt-get use the latest version in /var/cache/apt/archives/ ?
[I have a specific use for this *NON_STANDARD* behavior.]