
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given the parabola $C:x^{2}=4y$, a line passing through the point $M(0,2)$ intersects $C$ at points $A$ and $B$. A line parallel to the $y$-axis is drawn through point $B$ and intersects line $AO$ at point $D$. An arbitrary tangent line $l$ (not including the $x$-axis) of the parabola $C$ intersects the line $y=2$ at point $N_{1}$ and intersects the line $y=y_{D}$ at point $N_{2}$. Calculate the value of $|MN_{2}|^{2}-|MN_{1}|^{2}=\_\_\_\_\_\_\_\_\_.$

Present the answer in LaTex format: \boxed{Your answer}
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