In the "River Song's timeline" minisode / narrative story, Melody uses all her remaining regenerations to restore Doctor's life, after she first killed him with poison from a Judas tree. Melody now becomes River Song. Narrator says directly:

River: But I was shown who River Song would be and I saw just how much I would love him.

And so I gave all my remaining lives to restore his.

Because I knew the Doctor was worth it.

(...)

But she also mentions moment earlier:

I escaped the space suit and lived on the streets homeless, alone and dying until I regenerated.

That's one regeneration we can be sure of. My questions are:

• Did River Song had full 12 cycles of regenerations?
• How many regenerations were used to restore the Doctor to life? Why was more than 1 required?
• 2nd question leads to this one: Why she couldn't regenerate after the sacrifice in the Library?