Best practice would be to use the same version of TestComplete as TestExecute. But as far as "supporting" a very old version would go, I am assuming that it is because your organization is no longer opting to pay for the maintenance fee, so you are no longer receiving the upgrades or the support. In which case, if you wanted "support" you could always file for a support ticket, but you won't be getting the "support" in the sense that you have a dedicated account manager and access to smartbear's internal personnel.
Best,
Justin Kim
