I2 make HI from I2 +2H----2HI, swim thinks that H come from the water, right?
You won't make HI from water and iodine alone. You will have a little I2 dissolve in the water. There are several ways to make HI from I2. They are noted in the stim forum faqs, in threads, and at Rhodium's site. Common methods include using red phosphorous, phosphorus acid, or hypophosphorous acid with iodine to generate HI. Another is by using KI and phosphoric acid. There are other methods. The writeups are available with a little searching.
Right now I might suggest you read more and reason less. The answers to your questions are already here if you look for them. The wheel has been invented; modifications are welcome, but reinvention is likely not needed.