Be careful what you ask for...
Guppy:
You can ask for an SO course or the DEFO course. Depending on where they have more vacancies (assumig you have the experience for both) will depend on how open they are to placing you. Some have asked and been told no you are interviewing for DEFO others have asked and been been hired as SOs. If they call you for an SO interview though probably won't consider you for DEFO.
Yes you can fly in off time. As long as it does not infringe on hourly duty maximums and it needs to be ok'd with management. I know several pilots who do a little legit flying on the side.
Time between interview and hire can vary. If you are a prime candidate you can get in qiuck, if they like you but not asmuch as some of the others in the que (read Line up!!) then you may wait longer. Good thing is that they wil tell you whether you are hired or not. Unlike some airlines with hiring pools where you might never hear a thing!! Check out thread in wannabe fragrant forum.
FG