I'm pretty new to this, so forgive me if this is a silly question.
What I'm looking to restore is:

- The 2014 version of Deepin Desktop Environment

- Deepin Music 2.x

While I do like Deepin 15.4 a lot, I think the desktop environment and the music player are significantly worse than they used to be.

I have attempted restoring the old desktop environment in the past, but I didn't get very far due to missing dependencies.
As for the music player, I believe I did succeed in installing the old version at one point, but it failed to launch.

Any help would be greatly appreciated.

dependencies: that is the major problem with mixing versions of items within the OS. Especially shared dependencies. If you got one thing needing a ver 3 dependency and you want a different item needing the same dependency at ver 1.2 then you have a conflict within your system.

Most people that write their software (dependencies) when the change is made then the old goes away to make room for the new.
I think the best you could do is install an older version of Linux all together. I know Slackware keeps a entire copy of their old versions on a sight and mirrors trough out the world.

Everything that came with them. You'd have to investigate.