A:
I don't see any limitation in the specs. All software has limits. It is the nature of the beast. Since they say unlimited activities in the marketing material, I would assume the limit is a large number. Software boundaries/limits are usually a power of 2. I would assume the lowest limit would be 256 (2 to the 8th) but usually variables limits are ~2 billion.
You can try to contact Harmony support. They have been really responsive to me when I had questions.
I actually had a question on how to get my new LG TV to go directly to Netflix instead of bringing up the app selection screen. They pointed me to the documentation and also changed my setting for me. I just had to re-sync the remote and everything just worked. Their support is some of the best in the industry.