
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 vectors $\overrightarrow{a}=(-1,2)$ and $\overrightarrow{b}=(2,\lambda)$.<br/>$(1)$ If $\overrightarrow{a}∥\overrightarrow{b}$, find the value of $|\overrightarrow{b}|$;<br/>$(2)$ If $|\overrightarrow{a}-\overrightarrow{b}|=|\overrightarrow{a}+\overrightarrow{b}|$, find the value of the real number $\lambda$;<br/>$(3)$ If the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$ is obtuse, find the range of values for the real number $\lambda$.

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