Salam to all respected members

As you all know, many people appear for second attempt of CSS before the result of the final allocations of the first attempt is given by FPSC. (for example, if we appear for CE 2017, we will have to appear from CE 2018 before the allocations are made for CE2017).

My question is, what if someone is allocated to a group, say OMG, and then in the result of CE2018 she / he again clears the exam. Will the said candidate be able to improve his / her group or will this attempt be null and void? I know that officers are not allowed to appear in CSS during training. But what about the application process that is still in progress when one joins the academy?

Many thanks for your kind response.