Building previous version of px4

I am trying to build pixhawk earlier releases. I have choosed "ardrone_flight "code version which is one of the initial relaease as i am naive to understand current complex code structure. I am hoping to upload this code on pixhawk 1 but getting errors in build.

Ha! What is your incentive with this?

We’ve come along way since then, and I don’t think you’ll have much fun with that old state, unless you want to re-find old bugs or do a couple of years of development.

Actually i wanted to learn px4 firmware. Starting from earlier releases with less complexity seemed good idea. My goal is to understand px4 from scratch with nuttx.
Could you help me with how to remove these errors for clean build. Also is this firmware version compatible with pixhawk 1.(px4fmu-v2)

I think it’s better to learn about it using the current state. The older state will teach you something completely different, and without documentation matching it.

And no I really won’t invest time into making an old state compile again that is many years old, sorry.