According to the HART TP-Data Link Layer Spec-081 (FCG TS20081), devices must give out the response in STO time (~255ms), with the response code to indicate if this command was executed correctly or not.
For a READ command, such as command 1 or 2, you can respond with the last value of dynamical variables and with response code "08 - Update failure", so the host can decide to discard this value or not. But for a WRITE command, it's better to use the response code "32 - Busy" or delayed response mechanism (DRM) to let the host know the device is not ready yet, and should not just respond to the received data with a response code "00 - Correct" that would mislead the host.
More details about DRM, please see HART Spec-307 (FCG TS20307) Section 7.