
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 an ellipse $E$: $\dfrac {y^{2}}{a^{2}}+ \dfrac {x^{2}}{b^{2}}=1(a > b > 0)$ with eccentricity $\dfrac {\sqrt {3}}{2}$, $A$ and $F$ are respectively the left vertex and the upper focus of the ellipse $E$. The slope of line $AF$ is $\sqrt {3}$. Line $l$: $y=kx+m$ intersects the $y$-axis at a point $P$ different from the origin, and intersects the ellipse $E$ at two distinct points $M$ and $N$, with $\overrightarrow{MP}=\lambda \overrightarrow{PN}$.
- (Ⅰ) Find the equation of the ellipse $E$;
- (Ⅱ) Does there exist a real number $m$ such that $\overrightarrow{OM}+\lambda \overrightarrow{ON}=4 \overrightarrow{OP}$? If so, find the range of $m$; if not, explain why.

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