The INCORRECT statement is :

Options

A. LiCl crystallises from aqueous solution as `LiCl.2H_(2)O`
B. Lithium is the strongest reducing agent among the alkali metals
C. Lithium is least reactive with water among the alkali metals
D. `LiNO_(3)` decomposes on heating to given `LiNO_(2)` and `O_(2)`

Explanation

To solve the question, we need to analyze the statements provided and identify the incorrect one. Let's break it down step by step:

### Step 1: Analyze the first statement
**Statement:** Lithium Chloride crystallizes from aqueous solution as Lithium Chloride dot 2 H2O.

**Analysis:** This statement is correct. Lithium Chloride (LiCl) does crystallize from an aqueous solution as a hydrate, specifically as LiCl·2H2O.

### Step 2: Analyze the second statement
**Statement:** Lithium is the strongest reducing agent.

**Analysis:** This statement is also correct. Lithium has a high oxidation potential and is indeed considered one of the strongest reducing agents among the alkali metals.

### Step 3: Analyze the third statement
**Statement:** Lithium is least reactive with water among the alkali metals.

**Analysis:** This statement is correct as well. Among alkali metals, lithium reacts with water more slowly than the others, making it less reactive in this context.

### Step 4: Analyze the fourth statement
**Statement:** Lithium nitrate decomposes on heating to give lithium allyl.

**Analysis:** This statement is incorrect. Lithium nitrate (LiNO3) decomposes upon heating to produce lithium oxide (Li2O), nitrogen dioxide (NO2), and oxygen (O2), not lithium allyl.

### Conclusion
After analyzing all statements, the incorrect statement is the fourth one regarding the decomposition of lithium nitrate.

### Final Answer
The INCORRECT statement is: **Lithium nitrate decomposes on heating to give lithium allyl.**

---