There are no changes to the timing of what rows are visible and when. It will still be T-80h when row 4 would potentially but not always become visible to a platinum/gold/etc.
The mix of status pax and their PCV scores on the flight will continue to determine what rows are visible, eg. on a elite-lite flight, row 4 will likely be visible to most if not all pax, whereas on a elite-heavy flight, row 4 may only be visible to P1 or a high PCV platinum.
The key change for non-P1/CL/CLP1 pax is that instead of row 4 being free to select at T-80h, it is now chargeable.
As per above, yes, row 4 will remain blocked to platinums and below until T-80h.
QF - yes (only P1 get them free)
BA - no (emerald and above get them free for long haul, sapphire and above get them free for short haul)
AA - no if you're a JL/QR/BA/AA/IB/AS/AY elite (sapphire and above get them free), yes otherwise
JL - no (ruby and above get them free)
CX - no (sapphire and above get them free)
MH - yes (only MH platinum gets them free at OLCI)
AY - no (emerald and above get them free)
QR - no (sapphire and above get them free)
UL - yes (no one gets them free)
AS - yes (only AS/AA elites get them free)
IB - no (sapphire and above get them free)
AT - no (ruby and above get them free)
RJ - yes (no one gets them free)
That is my expectation of what will happen, although it won't be a free for all. It will still be gated by the status/PCV-based seat blocking depending on how elite-heavy the flight is.
Given that the status/PCV-based seat blocking is already in play at T-80h anyway, I'm not expecting a huge shift in row 4 availability. The timing will simply move from T-80h to T-24h.
Correct.
This won't happen - see the start of this post.
There's no other changes to T-80h other than the fact row 4 will be chargeable between T-80h and T-24h. This period will still be subject to status/PCV-based blocking controls.