This page will explain a few things about mod versions and some other important things you may not know about. You can find some videos here that explain things more in detail about some subjects related to mod versions from NorthWestTrees Gaming's YouTube channel.
Table Of Contents
Developing for Older Minecraft Versions
When you start working on a mod, it's always best to start with the latest Minecraft version available as many procedures blocks are not supported in older versions of MCreator.
Mods for 1.12.2
Keep in mind that trying to develop for 1.12.2 is not recommended, the community-run plugin has been abandoned and has many issues on its own. However, the java version for 1.12 is so far outdated that many issues can appear with MCreator causing more issues when trying to develop for this Minecraft version.
Minecraft ID Flattening
Also, keep in mind that 1.12.2 was before ids were flattened to strings which can cause more issues for compatibility than 1.13 mods when they implemented the flattened ids system.
Porting your Modifications
When you port your modification you can expect an influx of people to download your modification, in the case of your mod being published on Curse Forge this can increase your points which can be turned into Amazon Gift Carts or PayPal currency.
Porting your mod can also help with expanding your modification reach across more than one version of the Minecraft modding community, allowing for more people to use your mod and boosting downloads over time.
Porting to Older Versions
Often the java version will update which can sometimes make older versions of mods incompatible or cause many inconvenient issues to occur when porting.
Development Cycle and Progression
When you work on your versions and port to new versions you don't need to keep developing for older versions, often this can cause more work than any single person can handle, if you plan on adding support for different versions then you will want to make dedicated workspaces and GitHub repositories for each supported version so that you don't overlap the files for each version.
The Standard Approach
The option that many people take is to drop support after porting to a newer Minecraft build, this can save work but also cause fewer issues when trying to design procedures and make your mod mostly synced between multiple versions.
A video will be made on this soon by NorthWestTrees gaming.
GitHub Desktop Collaboration
It is possible to collaborate using GitHub's Desktop application by backing up your entire workspace folder and using Pull Requests to collaborate on a single project. Using this method can be more stable than using the built-in remote workspaces but does require a bit more experience with GitHub and repositories.