I would recommend against starting a question with "since."
At what age did you begin devoting yourself to sports?
How old were you when you started to devote yourself to sports?
How long have you been devoted to sports?
Would be the most common way to ask questions of this nature in English.
EFL learners use 'since' far too often, I agree. French speakers, for example, often fall into the trap of using it in the way that 'depuis' is used in French.
But it is sometimes correct in a question - I would recommend only using it in a 'since when...' construction, unless you are fluent.
For example, in the sentence given, "Since when have you devoted (or 'have you been devoting') yourself to sports?" is a more natural English question.
Directly answering the post, 1) is certainly wrong, and 2) is OK. Mykwyner's alternatives are more natural though.