In Book One Canto Five, Aswapati saw ‘a golden ladder carrying the soul🔥, / Tying with diamond threads the Spirit’s extremes. In Book Two, Canto One the world stair is discussed in detail. 1) Is this stair the same as the golden ladder, one that connects the Inconscience to Superconscience?

Yes it is the supramental link that connects the One to the Many, the Creation to the Creator. 

2) Ashwapati breaks out into another Space and Time to be able to see this World stair. Does that mean that we cannot see it while remaining in this world?

Yes we can experience its different energies and effects but to see it one has to emerge into the fourth dimension.

3) Also, this stair is described as one whose bottom is viewless and the top is viewless too. Is it the column of endless light described in the Puranas?

Yes because it is the infinite Mother who has become these worlds. While the worlds are limited and finite, their origin is infinite and extends from the Supermind to the Inconscience. 

Affectionately,

Alok Da