
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
Read the calculation process of the following student and complete the task.  
Simplify first, then evaluate: $[\left(2x+y\right)\left(2x-y\right)-\left(2x-3y\right)^{2}]\div \left(-2y\right)$, where $x=1$, $y=-2$.  
Solution: Original expression $=(4x^{2}-y^{2}-4x^{2}-12xy+9y^{2})\div \left(-2y\right)$, Step 1  
$=(-12xy+8y^{2})\div \left(-2y\right)$, Step 2  
$=6x-4y$, Step 3  
When $x=1$, $y=-2$, the original expression $=14$, Step 4  
$(1)$ The multiplication formula used in the first step is ______ (write down 1 type is enough);  
$(2)$ An error occurred in step ______ of the above steps;  
$(3)$ Please write down the correct solution process.

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