I can't remember the specifics, but VOT or COT to a different trade can come with a demotion when you aren't meeting the specific trade requirements for the current rank, but there is something about keeping the rate of pay, and just not increasing until you get back there in the new trade.
Vested rights, so one who remusters keeps the old rank pay if they get knocked down to Cpl.
I've heard of two demoted sergeants having their pay protected.
Granted I didn't go around getting demoted willy nilly, so I'm not 100 percent sure if that's accurate.
With the caveat that I got out at the end of 2004, so this may not be current.
All personnel sentenced to detention lose their rank for the period of detention as far as pay goes, but your rank stays on (well on the CF's for inspection layout, wearing for church parade), you used to receive a $1 a day allowance for upkeep expenses, but IIRC you got paid at PTE(3) while you where in (just no access).
Unless you got sentenced to demotion, or loss of seniority, when you get out you are back up to your rank pre sentencing.
CO's could do 90 days BD, as well as demoting or loss of seniority, then it because 30 days, anything above 30 Days needed a CM.
IIRC anything over 14 days needed to be approved by the Bde Commander.
WRT to pay protections, pay could be protected IF there were previous allotments (child support, alimony, etc) or an unreasonable hardship, but speaking from experience, all they do is claw it back once you get above a threshold.
So if you where a Sgt(2) and got busted to Pte(3), you may have been getting something close to a Cpl(4) due to protections, but you are actually in the hole a significant amount, and the CAF keeps track to ensure they get their money back - so if you get back to Sgt, you would likely be seeing still close to Cpl(4) and seeing a lot of deductions until you are square with the accounting system.
Also if your CO was a fuckwit and doesn't understand the powers of punishment, and only sentenced you to DB, and decides after you get out of DB that he really meant to also demote you as well, and then because the next CO is even more inept with Admin that you stay longer as a Pte than the first time you where a Pte, well then you probably where in a Militia unit in the 1980-90's, especially if the pay system realizes after summer that you got paid at your old rank and decides not to pay you at all for 7 months, regardless if the RSS Admin Clerk keeps telling them they can't do that, and that there is zero record of any demotion either...