HI Sid,
CORE uses 4.2.
There is no deprecated Unwrap method.
The one-click Unwrap used the Angle Based, as I mentioned above. The Adjust Last Operation box (also available with the F9 key) let’s you change that, as shown in my screenshot above(left in 4.2, right in 4.3).
So, in 4.2 we had:

And in 4.3+:

And look again at my other Screenshot with the Adjust Last Operations Panels.
It’s, like I already said, a simple re-ordering of options and one new one.