I haven’t found any information on is it possible by using C/FRONT from 5.0 package to open 3.X and 4.X databases? I’ve tried to open 4.3 database with 5.0 version of C/FRONT and it was working but sometimes with crashes without any reasons(sql CFRONT). Maybe somebody has tried this and can save time on tests?
With Native, it is rigidly controlled, but with SQL its as you said, it will work sometimes and sometimes crash. If you want this to be reliable, then unfortunately you really do need to have the Client and server matching.
Yes - the client and server version generally have to match exactly:
In our tools we load the cfront.dll or cfrontsql.dll dynamically (using LoadLibrary function - this is what its called in C at least). In this way we only have to ensure that we place the correct cfront.dll (and associated files like dbm.dll etc) in our program directory and so we can support all versions of Navision with the same compiled version.