Originally Posted by
GetSetJetSet
Depends on what class. If you want J or R on the SQ A380 you're out of luck. Otherwise, stopover (JFK), destination (CDG) and open jaw are all definitely allowed.
SQ C on the A380 is permitted. F is not as a general rule because it is "Suites."
The OP's routing is fine. Changing the flight will incur a fee if inside 21 days unless you waitlist the desired segment in advance. You can do that after the reservation is confirmed so long as the pending segment is UA metal.