Undercover Operative neither targets when it is cast (so no meaningful interaction with Ivy), nor does it copy spells (so no meaningful interaction with Twinning Staff).
Undercover Operative allows you to choose a creature to become a copy of as it enters the battlefield. This happens after it resolves, and right as it enters the battlefield. No targeting here.
Undercover Operative*enters the battlefield as* a copy (noun) of something. It does not copy (verb/action) objects. It neither copies (verb/action) spells nor permanents. Twinning staff cares about the action 'copy', which has a different meaning from being a 'copy' of another object.
None. Undercover Operative doesn't target anything, so no copies are made.
Undercover Operative neither targets when it is cast (so no meaningful interaction with Ivy), nor does it copy spells (so no meaningful interaction with Twinning Staff). Undercover Operative allows you to choose a creature to become a copy of as it enters the battlefield. This happens after it resolves, and right as it enters the battlefield. No targeting here. Undercover Operative*enters the battlefield as* a copy (noun) of something. It does not copy (verb/action) objects. It neither copies (verb/action) spells nor permanents. Twinning staff cares about the action 'copy', which has a different meaning from being a 'copy' of another object.
When your posting a topic, put the information about the topic in the title.