
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 a quadratic function $y=-x^{2}+bx+c$ where $b$ and $c$ are constants.  
$(1)$ If $y=0$ and the corresponding values of $x$ are $-1$ and $3$, find the maximum value of the quadratic function.  
$(2)$ If $c=-5$, and the quadratic function $y=-x^{2}+bx+c$ intersects the line $y=1$ at a unique point, find the expression of the quadratic function in this case.  
$(3)$ If $c=b^{2}$, and the maximum value of the function $y=-x^{2}+bx+c$ is $20$ when $b\leqslant x\leqslant b+3$, find the value of $b$.

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