I am on a current modern PLM on my esiy.

I recently got a lot of older parts from ebay which included many USB and Seriel PMLs, some are quite old, all 2413U and 2414U

Knowing the future is Insteon is uncerten ( hope not, but not sure they are that popular anymore and their devices cost much more) I'll keep a few of these as spares, but a few questions.

1. Can IOX restore from a newer to an older PML?

2. Is it no issue to go between serial and USB PLMs? (I have never used USB)

3. Is there an easy way to test these PMLs to see if they are good or if some need re-capping or or just dead? Or is it really just wait until it's needed and if it works it works?

2414U is not a PLM. It is PLC Power Line Controller. Could have programs downloaded in to it and run on its own. You had to create a program. Then use their compiler to compile it and down load it to the 2414U OR 2414s. With the SDM Smarthome Display Manager running the program. I believe it was Windows only.

2413S and 2413U are the same except the interface daughter board to the outside world. If sent the PLM ID command. It will have a different Subcategory. Most programs I know of did not check it and still worked fine. Subject to the known capacitor issues we have seen in the older revisions.