Yes.

Fire the shot as normal. If the template ends up over any models in a unit that have been augmented by Pha's Protection roll a D6. On a 4+ the entire shot is discounted.

Yes.

No. As long as a spell is cast while Throne of Vines is in play then the spell gains the additional benefits until the spell ends.

Any models that do not have space to be placed at the back of the unit are lost. If, for example, your unit has been charged in its rear facing then you would be able to complete the back rank and any excess models are lost.

No, but remember that the unit will still count as having charged when working out the combat result. (Reference)

The unit can still be increased back to 20 models. You can resurrect the model that was carrying the standard as a rank and file model.

Yes.

They are considered unable to move and suffer D6 Strength 3 hits.

Yes.

Yes.

Yes.

A Wizard can use the Breath Weapon up to once each time he has successfully cast the spell (whilst he is still transformed of course!).

No.

Yes.

Yes to both question. Though it is worth noting that a test is not required if he leaves without moving, through the Smoke and Mirrors lore attribute for example.

Yes, however far they can normally move, it will be doubled. For example, a unit with the Random Movement (2D6) special rule rolls a 9. This would then be doubled to 18.

Yes.

It will affect both.