ISU AP definitely does deflection damage
You need to check the commander revamp changelogs when you do these searches. For some reason some of the changes that went live from those previews are NOT in the main changelog but they are definitely in the game. You will find the deflection damage change in the December Commander Revamp
Can I ask why you don't play the game anymore? Cause you would know it does deflection pretty easily if you used it once since the change
Yep, you have to basically check 2 other threads outside of the normal changelog to see for other changes, mostly focused on doctrinal units.
OR you can also check on the coh2db site.
TBH, if you don't play teamgames, you won't see ISU152 at all. And ideally you would never want to use it on AT mode.