Documented Techincal Differences Between SE & OnLine

I am engaged in a project that requires scaling down a software package that was developed for the OnLine engine to work on SE. Although thus far in the project I have discovered VERY specific differences (or limitations) that exist in SE as compared to OnLine, I am looking for a technical reference that may document ALL of these differences. I am hoping to investigate and resolve each of these documented issues in my software and then test the results.... rather than depend on finding these differences solely through a test effort. I have been told documentation of this kind is available somewhere.........It is already apparent that the number of elements you can index and select on in SE is lower than OnLine..........8 vs 16. I would appreciate any information, pointers, advice, etc. that anyone reading this request may have to share. Thanks in advance for any help you can provide. rlj@gate.net