The 'new' Elephant enclosure is actually the original White Rhino barn which housed their very large herd of White Rhinos in the past. It was then refitted out for the Elephants, with large paddocks and a seperate(new) Bull barn plus sandyard etc were also added.
I can't remember when it opened with Elephants.
I believe the decision to keep/breed Asian Elephants over Africans was based on their relative numbers and decline in the Wild.
This is definitely Jumbo, the African forest bull from Whipsnade. The ears are small/rounded, downward pointing tusks, the back is straighter than the bush species, and this one has typical cyclotis facial features. The premaxilla region and head shape also indicate its a male, though he looks a bit overweight.
I've seen several other images of Jumbo and can conclude this is the same animal.
The African in the background is a female africana.