RadioRA and RadioRA Classic are interchangeable. It was not referred to Classic until release of SR or 2. I think that the initial launch was around 1998.

RadioRA Classic, RadioRA-SR and RadioRA 2 are all independent systems and you can't mix parts. If you have a main repeater for each system you could mix old and new systems using the proper accessories and likely another control system to supplement the scene control.

RadioRA-SR was a Single Room system and basically a stripped down version of RadioRA 2, but completely incompatible. I think this launch was around 2008.

I'm not positive but RadioRA-SR was released during the anticipation period of RadioRA 2. RadioRA-SR was never PC programmable by dealers afik. It was marketed to residential dealers for use in standalone rooms such as home theaters; most refused to sell the system because it was not expandable or compatible with RadioRA 2. The product found the most traction in the hospitality area but has been discontinued probably because RadioRA 2 is a far superior product and the price points were nearly identical.

RadioRA 2 wasn't PC programmable at the initial launch and the manual configurations could not be imported into the software once it was released. RadioRA 2 was PC programmable shortly after launch and it became a very tough system to beat for small to medium installations both retro and new construction.