Can the side door be on either side?

Yes, you are able to install the sliding door to any side of the wall, just to be sure the A2 and B2 are always installed next to each other, please refer to the Assembly Manual in following link,

https://drive.google.com/file/d/1a2b3rboVIlEp3xPq54D1Zi5faIyPTGSs/view?usp=sharing