That frozen meat is not reliable. Merely by stamping halal it should not be halal and one should avoid eating it.
(2) If the chicken is taken out after slaughter after a few minutes in order to soften its skin while the water is not so hot, then this method is correct and the meant will remain pure and halal to eat. Yes, if the chicken is put in hot water for a long time that its entrails are dissolved in the meat then the meat of the chicken will turn haram and impure. It is not lawful to eat such a chicken.
Allah knows Best!
Darul Uloom Deoband