Sunbeam Spell - a little confusing?

[Schade]

The wording of this spell confuses ma a little - I would appreciate any clarification.

Can you cast a beam in the first round you cast the spell - or do you have to cast the spell and use your standard action - and then only in subsequent rounds you can cast the beam?

If my caster level allows me 3 rounds - can I only cast one beam per round during the duration of the spell? Or can I let fly with 3 beams at once?

Does the blindness end when I cast the last beam because the spell ends? Or is it permanent?

[Calth]

Answering your questions 1 by 1

1.) RAW, you don't get a beam from casting the spell, only subsequent standard actions generate them

2.) Only one beam per standard action, and remember you only get 1 beam per 3 caster levels, so if you have three rounds you only have one beam(this is a poor example since you need to be 13th level to cast the spell, so 13 rounds and 4 beams minimum.)

3.)The blindness is permanent if the target fails its save.