Can You Explain What kind of application you Use? If you use some kind of database with your application then simply run delete query with some specific condition

Simple way to delete users account?
I need the update manager to only download a single package at a time and not try to download multiple packages at once.

My slow internet cannot handle multiple connections; slows the download to a crawl and some packages will reset themselves halfway through when they time-out.

EDIT

When using apt-get update multiple repositories get checked:


When using apt-get upgrade multiple packages are downloaded:

