Sergey,
Here is what I have observed so far:
1. An exe compiled under VFP 9 will run with a VFP 7 runtime if it is called with 'Do command'
2. A VFP 9 specific command entered into a VCX and compiled under VFP 9 will run without error if included in a VFP 7 exe.
3. The same VCX compiled in VFP 7 reports an error when run, but not during the compile process.

Conclusion: This is crazy. This is not operationally important but I would like to have some technical understanding of what is going on.