Hello lucky one. 
1. Yes but very few. OCT, IMO, will not let you experience your SPF
life, as they tend to be posted to do office duties due to their
rank.
2. After BPT you'll get posted to different units where you will
receive more specialised training. (Eg. SOC go SOC course, NPCO go
NPCO courses etc) Progression will depend on your appraisal
9-12mths after you POP and get sent to your unit. Prior to your
promotion you'll go for a 1 week course after which you'll most
probably have your Sgt rank.
3. IPPT you'll need a silver to be qualified for the more
interesting vocations.
Whatever you do, don't apply for the Field Instructor post, which
will make you miss out on the ground life.
NPCO will be fun if you like to experience the real world, where
drug addicts, kiddy bengs and illegal immigrants will be your
prey.
Good luck.
