After full recovery... Is there any physical activity that we r not supposed to do having the band? I know this might sound lame but is there a heavy activity that can harm us or the band? make it slip or something

No, your band is well protected inside your body. There is no normal activity that should damage it.

The only one I can even think of possibly happening is depending on how well the DR stitched your port to your ab muscles if you do a lot of crunches or something it might cause it to flip but I would think that would be a rather rare issue and you would have to do an insane amount.