Yes, this has been rolled out to all users from today (was available for a smaller set of users last week)
Now will be able to unpledge cash equivalent securities by directly selling them without needing to manually unpledge them first. But similar to stock collateral behaviour, first the quantities will reduce from pledged holding followed by the free holding due to the OMS vendor limitations.
Yes, 80% margin will be available instantly after selling the pledged holdings.