The developmental sequence for questions by L2 learners is similar in most respects to L1 language acquisition (* Please see pp. 7-8).
The developmental sequence for questions, while very similar across learners, also appears to be affected to some degrees by L1 influence (e.g., German learners of English, p. 79).
Stages of forming questions (see examples on p. 79):
stage 1 – single words or sentence fragments
stage 2 – declarative word order (no fronting and no inversion)
stage 3 – fronting (wh- fronting but no inversion; do-fronting)
stage 4 – inversion in wh- + copula and ‘yes/no’ questions
stage 5 – inversion in wh- questions
stage 6 – complex questions (tag questions; negative questions; embedded questions)