Learn Swedish: Lars, han är framgångsrik men fortfarande singel.

This is called left-dislocation. You state the topic (Lars), pause, and then use a pronoun (han) to represent him in the actual sentence. It puts heavy emphasis on Lars as the focus of the conversation. This structure is very common in spoken Swedish and casual writing.

Doesn't the V2 rule mean the verb är should come immediately after Lars?

That would be true if Lars were the subject inside the clause. However, in left-dislocation, the fronted topic (Lars) sits entirely outside the main sentence structure. The actual main clause starts with han (position 1), so the verb är is correctly in position 2.

How is the word framgångsrik built?

It is a compound of framgång (success) and the suffix -rik (rich). Framgång itself comes from fram (forward) and gång (movement or walk). So framgångsrik literally translates to 'rich in success'.

Can I use singel for anything that is 'single', like a single ticket or a single item?