Say it's just like normal speak with dead but doesn't need a body and instead summons a "spirit" (not the person's actual soul, more like an "echo" left behind by psychic impressions and the like from when they were alive) to answer the questions and only requires you be in place important to the deceased's life when you cast it. What level would it be?
Probably 2 levels higher than regular Speak with Dead, at least for Clerics and such. Probably 1 level higher for Inquisitors.
So probably something like cleric/oracle 5, inquisitor 4, medium 4, psychic 5, shaman 5, spiritualist 5, witch 5. At least for the initial starting point.
I'd have to go refresh my memory on Mediums, Psychics, and Spiritualists. Maybe Witches, too.
That really depends on the quality of information given. Spells that give similar information and with similar (lack of) restrictions are a good guideline. Let me suggest:
Akashic Communion is mostly a skill boost, but it can provide information about a specific incident at the GMs discretion. That is the GM making the spell go beyond its description, so if you want a spell that does more normally, it should be higher level. So this really should be considered weaker than the proposed spell.
Contact Other Plane again provides a lower quality level of information. The short answers are a huge restriction. Also the high chance that low danger sources don't know the answer or are going to intentionally lie means this is a spell of questionable value or high risk.
Legend Lore seems appropriate for comparison. It is information of about the same quality. There are rules for asking about things you only know about without having the subject present. It doesn't have any ability to ask questions so...it might be appropriate to raise the level by 1 for the proposed spell. I'd also recommend including some way to prevent this spell from getting over used. Something like if the spell is cast by the same person more than once a week they have to make a save or gain a spellblight, with the DC growing the more times they cast and the potential spellblight growing with each casting.