Hi, thank you for contacting JustAnswer.com. My name is Russell. I will try to do what I can to provide the right answer to your question.
Though your question is somewhat a mix of many concerns, that I can see, it nonetheless has some answers:
1. you have reached JustAnswer.com, not LG, unfortunately.
2. if you have an LG phone in which the battery has failed, then either
- if within warranty, the phone and battery may be taken to an LG shop and repairs under warranty (probably free-of-charge) may be made there (provided you have proof-of-purchase-date e.g. a sales slip for the phone.)
3. if there is some offer regarding a free phone, I do not know of one.
4. I know of no 'knock code' for LG3, I regret to say.
(I regret that I am not able to offer Live Phone Call service at this time; However, your request is still open to other Experts in this category, and one of them may pick up on it at any time.)