I have a Do-More app developed about 2 years ago. Should there be any problems using the new version of Designer and installing it into a new Do-More PLC?
No. The only possible concern is that once you save or download the project with the new version of Designer, the project file and the project in the PLC will not be able to be opened by the OLD version of Designer. But since Designer is free - you don't have to worry about making sure all your PCs have that version of Designer.
You may need to update your PLCs firmware if you decide to utilize any new Do-more Technology features that were added. Look at the Updates.pdf to see the latest features (click on the
What's New star at the top of the Start Page). Some features are Designer side only, some also require new firmware (e.g. new instructions) .