I noticed them advertising a 1 time only SSR guaranteed gacha. I am confused by what "one time only" means. Does it mean limited time, like the offer will disappear in a week, or does it mean I can only buy 1 ticket? If only 1 ticket, will that reset at a later date?

Also, if I can only afford 1 ticket 1 ticket, should I buy the kamihime ticket, since they are harder to get at SSR level, or should I gamble and try to get a 100 percent eidolon?

Thank you.