You can check the release notes to see if you're using functions that were introduced in R2018a, but I suspect from your description that everything should compatible.
Things to watch out for in terms of compatibility are .fig files (avoid if possible), Simulink models, and complex interactions with graphical elements. The wider the gap in time between the releases you want to be compatible with, the more important these considerations become. Forward compatibility is usually a lot better than backward compatibility (with big jumps in R13 to R14 and R2014a to R2014b).
