Uhh.... you did mention you wanted to learn what all the techs do. I merely pointed out there is no method to unlock all techs while playing one species.
- Enable cheats
- Pick a species
- Hit CTRL-R
- You now have access to every technology available to the species
- Rinse repeat for the next species
Many species share technology so the list of differences is isn't big. For example: The Terrans, Drath, Altarians, Torians, Korx and Krynn have more similarities between their techtrees than not. However, they can be connected differently.
Alternatively you can load up the scenario Battle of the Gods.
I hope this helps.