Pick out the correct statement(s):

Options

A. `MnO_(2)` dissolves in conc.HCl but does not form `Mn^(4+)` ions
B. Decomposition of acidic `KMnO_(4)` is not catalyst by sunlight
C. `MnO_(4)^(2-)` is stongly oxidising and stable only in very strong alkali. In dilute alkali, water or acidic solutions it disproportionates
D. `KMnO_(4)` does not act as oxidising agent in alkaline medium

Explanation

To solve the question regarding the correct statements about the properties and reactions of manganese compounds, we will analyze each statement based on the information provided in the video transcript.

### Step-by-Step Solution:

1. **Statement Analysis of MnO2 with Concentrated HCl**:
- The transcript states that MnO2 dissolves in concentrated HCl to form Mn²⁺ ions and does not form MnO₄⁻ or Mn⁺ ions.
- **Conclusion**: This statement is **correct**.

2. **Decomposition of Acidic KMnO4**:
- The transcript mentions that the decomposition of acidic KMnO4 is catalyzed by sunlight. However, it states that this statement is incorrect because KMnO4 does decompose under sunlight.
- **Conclusion**: This statement is **incorrect**.

3. **Stability of MnO4²⁻**:
- The transcript explains that MnO4²⁻ is a strong oxidizing agent and is stable only in very strong alkali. In dilute alkali or acidic solutions, it disproportionates.
- **Conclusion**: This statement is **correct**.

4. **KMnO4 as an Oxidizing Agent in Alkaline Medium**:
- The transcript indicates that KMnO4 does act as an oxidizing agent in alkaline medium, reacting with iodide ions (I⁻) to form IO₃⁻.
- **Conclusion**: This statement is **incorrect**.

### Final Summary of Correct Statements:
- The correct statements are:
1. MnO2 dissolves in concentrated HCl to form Mn²⁺ ions.
2. MnO4²⁻ is a strong oxidizing agent and is stable only in very strong alkali.