Award seats are released 355 days ahead. And most likely SQ will announce the first flight maybe 2-3 months or maybe 5-6 months ahead (and this is not guaranteed). So best will be pay cash.

for SQ22/24, these are new routes. Thus once they announce you will be able to get the award seats if SQ released.

for 777x they will most likely be deployed on current routes

my guess it will be Sydney. Since it only need 1 plane to do a same day return.