Wales stopped opting out at the end of August/early September that year when Wales Today moved to 6:30.
Northern Ireland carried on until at least 1991, though not sure on dates.
Northern Ireland carried on until 1996! Andi Peters says on the Broom Cupboard website that he thought saying goodbye to Northern Ireland every night was getting a bit dull, so he stopped doing it for a bit and just left a pause, but so many people complained he had to start doing it again.
Wales Today was at 5.35 from 1984 to 1988 because they shared a studio with S4C Newyddion which was on at seven, so there needed to be a gap between them. Seemingly that problem was solved in 1988, presumably Newyddion was rescheduled, and obviously Neighbours was a massive show at the time so they were presumably keen to show that at the same time as the network.
When the Six began in 1984, Inside Ulster was initially at 6.30 like all the other regions, but I've got the BBC Handbook from 1985 which said ratings plummeted in that slot so they moved it to 5.35 to avoid a clash with UTV, who were totally dominant in that slot. And they kept it there for the next decade, with Neighbours at 6.30 of course, and another Inside Ulster bulletin at 6.55.