Extract Behavior with Changes Only parameter as Blank

Summary

HCM Extract behavior when scheduled / submitted with Changes Only parameter set as blank.

Content

Hello, 

I'd like to know if anyone has come across / looked into this aspect of HCM Extracts - 

While submitting the extract, how would a changes only extract behave 
1) If the Changes Only parameter was left blank while submitting? 
2) If the default value for the changes only parameter was updated to a value, say BLOCK, after submitting the extract? (While submitting the field was set as blank)
3) If the parameter values were updated at Refine Extracts > Parameters tab to say BLOCK / BLOCK_OLD

We have an extract that was (accidentally) scheduled for a week in a similar manner and was hoping to look at options before I head to the Scheduled Processes to cancel and reschedule.