The incorrect order is:

Options

A. `N gt P gt As`: strength of `pi`-bond with oxygen atom
B. `SiF_(4) gt SiCl_(4) gt SiBr_(4) gt SiI_(4)`: Thermal stability
C. `H_(2)S gt H_(2)Se gt H_(2)Te`: Arrhenious acid character
D. `CaBr_(2) gt MgBr_(2) gt BeBr_(2)` Melting point

Explanation

To determine the incorrect order from the given options, we will analyze each statement step by step.

### Step 1: Analyze the first option
**Statement:** Nitrogen > Phosphorus > Arsenic (in terms of strength of pi bond with oxygen)

- **Explanation:** Nitrogen forms strong pπ-pπ bonds with oxygen due to its small size and effective orbital overlap. As we move down the group from nitrogen to phosphorus to arsenic, the size of the atoms increases, leading to poorer overlap and weaker bonds. Therefore, this order is correct.

**Hint:** Consider the size and bonding characteristics of the elements involved.

### Step 2: Analyze the second option
**Statement:** SiF4 > SiCl4 > SiBr4 > SiI4 (in terms of thermal stability)

- **Explanation:** The thermal stability of these compounds is influenced by lattice enthalpy. The lattice enthalpy decreases as the size of the halide increases (F < Cl < Br < I). Since the charges (Q1 and Q2) remain constant, an increase in the size of the anion (R2) leads to a decrease in lattice enthalpy, making this order correct.

**Hint:** Remember that lattice enthalpy is affected by the size of ions involved.

### Step 3: Analyze the third option
**Statement:** H2S > H2Te (in terms of Arrhenius acid character)

- **Explanation:** As we move down the group from H2S to H2Te, the bond length increases, resulting in weaker H-X bonds (where X is S or Te). This means that H2Te is a stronger acid than H2S due to its lower bond dissociation enthalpy. Therefore, the order H2S > H2Te is incorrect.

**Hint:** Consider how bond length and strength affect acid character.

### Step 4: Analyze the fourth option
**Statement:** CaBr2 > MgBr2 > BaBr2 (in terms of melting point)

- **Explanation:** The melting point generally increases down the group in the alkaline earth metals due to increasing ionic size and stronger metallic bonding. Thus, this order is correct.

**Hint:** Think about how melting points change with increasing atomic size in a group.

### Conclusion
After analyzing all the options, we find that the incorrect order is:

**H2S > H2Te** (Option 3)