Collection is one of those difficult terms that is used differently by different horseman and different disciplines.
Some horseman use the term collection somewhat loosely to mean a horse the is moving off their hind end, rounding up through the back and actively seeking contact.
While I recognize and accept that definition, I prefer the narrower, stricter, dressage definition of a horse that is all of the above things, but has also has an elevated ribcage, increased flexion in the joints of the hind limbs and appears to be traveling uphill as his hindquarters are lowered relative to the forequarters.
I don't think too many people would disagree that the second photo shows your horse moving and using himself much better than the other photos, however, I would call that on the aids, on the bit or connected, NOT collected.
However, it is mostly dressage riders who make that distinction.