Learn French: Le four est dangereux, ne vous brûlez pas ! - The oven is dangerous, do not burn yourselves!

In positive commands, the reflexive pronoun comes after the verb with a hyphen, like brûlez-vous ! (burn yourselves!). But in negative commands (telling someone not to do something), the pronoun moves back in front of the verb, just like in a normal present tense sentence. So it becomes ne vous brûlez pas !

Could "ne vous brûlez pas" also mean "do not burn yourself" when talking to just one person?

Yes! Vous can be plural ("yourselves") or a formal singular ("yourself"). The English translation here says "yourselves" so we know it is addressed to multiple people, but the French sentence is exactly the same if you are politely warning just one person.

How would I say this to a single friend using "tu"?

You would use the pronoun te and the tu conjugation of the verb: ne te brûle pas ! Notice that the verb is brûle without an "s" at the end. For regular -er verbs in the imperative command form, you always drop the final "s" for the tu form.

Why does "dangereux" end in an "x" if it is describing just one oven?

Adjectives that end in -eux, like dangereux (dangerous) and heureux (happy), naturally end in an "x" in their masculine singular form. They do not change in the masculine plural. If the noun were feminine, the adjective would change to dangereuse.