My understanding is Ven. Ananda was not a Sotapana before Buddha’s Parinibbana.
This is based on the following two Suttas.
“It’s amazing, lord, it’s astounding, how deep this dependent co-arising is, and how deep its appearance, and yet to me it seems as clear as clear can be.”
[The Buddha:] "Don’t say that, Ananda. Don’t say that. Deep is this dependent co-arising, and deep its appearance. It’s because of not understanding and not penetrating this Dhamma that this generation is like a tangled skein, a knotted ball of string, like matted rushes and reeds, and does not go beyond transmigration, beyond the planes of deprivation, woe, and bad destinations.
http://www.accesstoinsight.org/tipitaka … .than.html
Dependent Origination is seen in full with the attainment of stream entry:
“These are the four factors of stream-entry that he possesses.
“And what is the noble method that he has clearly seen and thoroughly penetrated with wisdom? Here, householder, the noble disciple attends closely and carefully to dependent origination itself thus: ‘When this exists, that comes to be; with the arising of this, that arises. When this does not exist, that does not come to be; with the cessation of this, that ceases. That is, with ignorance as condition, volitional formations come to be; with volitional formations as condition, consciousness…. Such is the origin of this whole mass of suffering. But with the remainderless fading away and cessation of ignorance comes cessation of volitional formations; with the cessation of volitional formations, cessation of consciousness…. Such is the cessation of this whole mass of suffering.’