Changing constraints to expand a view in swift iOS

I have a stack with 2 view inside it, the yellow takes up 70% of the stack and the green the other 30%. I want to code a button that will upon click:

1. Expand the stack to the top of the screen, which I have done via:

myStack.topAnchor.constraint(equalTo: view.topAnchor).isActive = true

2. Then make the green box take up the whole stack, so the screen will be completely green

I have done the 70:30 thing with "equal widths constraint like so: widths

How may I achieve this functionality and what is the code of resetting everything back to normal? desired output

1. Change the stackView distribution to be Fill Proportionally.
2. Set up width constraints indepedently for each view (with priority = 999, allowed to break). (0.7 of superview.width for first & 0.3 of superview.width for second).
3. Call firstView.isHidden = true, it will automatically stretch the secondView to cover stackView in full - Expanded state.
4. Call firstView.isHidden = false, it will bring you back to Initial state.