This was made in GB Studio 2beta5 but there is a build of that now available that allows you to export .pocket files.
Here it is Mack: https://github.com/BestPig/gb-studio#analogue-pocket-export
I will say from experience, that while it is hard to migrate a project to GBS3.0, the recent update has made it somewhat more efficient. The hitboxes in this game could benefit from the GBS3.0 treatment as you can adjust them rather than having a fixed 16x16 pixel hitbox. Its extra work but I feel this game is worth the effort, it's such a good example of what GB Studio can achieve!
On GBC exclusive content, you can change the file extension to .gbc but also it's a good idea to have an IF COLOR MODE ENABLED == flase, send the player to a scene that tells them this game is intended for GBC only. That's what I did on Cupid to make sure.