first question: did you actually purge the extras installation? (because I don't deem it necessary; I could've mentioned it before, though..).

regarding auto-update: 'autoupdateconfigurator' is the app to go (I think it technically can't 'disable' the auto-update entirely but can set the check interval to a really-really long period).
okay, 'back' after some 'research' . it's maybe not in the 'standard'-repos. check this page for a brief overview and here is the direct download link (it's a .install-file).
[edit]but the more knowledgeable should be able to directly point to the right config-file to manually <s>tamper with</s> alter[/edit]
[edit2]here one goes *facepalm*[/edit2]

regarding media-files you've got: you'll find them in "~/.purple/telegram-purple/+$YOUR_PHONE\#/downloads/". however, an alternative way is visiting 'tdesktop.com'. for windows, I'd recommend their portable version. copy only one (large) executable-file to any usb-drive/location you want and you're good to go. neat management of your profile, chat-history and all your media-files.

nice evening