Why does the PIV in centre tap rectifier is twice of the V source?

[sophiecentaur]

They are all correct, except for the last one. The error is tiny & trivial, but it should be
PIV = 2Vp(sec) - 0.7 V

Yes. Kirchoff 2 applies here. How anyone could imagine that a diode actually supplies emf escapes me.

All of this can be resolved by properly specifying the (multiple) output voltages of the centre tapped transformer.