
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
Determine the sequence numbers of the correct propositions among the following four propositions:

1. The chord length obtained by the intersection of the circle $(x+2)^2+(y+1)^2=4$ and the line $x-2y=0$ is $2$;
2. The line $y=kx$ always has common points with the circle $(x-\cos θ)^2+(y-\sin θ)^2=1$;
3. "$a=2$" is a sufficient but not necessary condition for "the line $ax+2y=0$ is parallel to the line $x+y=1$";
4. If the edges of a regular tetrahedron are all $\sqrt {2}$ and its vertices are all on the same spherical surface, then the volume of the sphere is $\dfrac {\sqrt {3}}{2}π$.

Write out the sequence numbers of all correct propositions.

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