Which of the following is not true for the given figure :

1. △ APC ≅ △ BPD

2. CP = DP

3. AB and CD bisect each other

4. all of the above are true

From figure,

In △ PCA and △ PDB,

⇒ AC = BD (Given)

⇒ ∠PCA = ∠PDB (Both equal to 90°)

⇒ ∠CPA = ∠DPB (Vertically opposite angles are equal)

∴ △ PCA ≅ △ PDB (By A.A.S. axiom)

We know that,

Corresponding parts of congruent triangles are equal.

∴ CP = PD and AP = PB.

Thus, we can say that :

AB and CD bisect each other at point P.

Thus, all options are correct.

Hence, Option 4 is the correct option.