Answers to your 3 questions:
1) No, there is no such "magical" device. If there were, everyone else would know about it too. When a battery is past the end of its service life there is no process to revive it.
2) Moot question in light of the first question.
3) I'm going to speculate that the initial test was faulty. The dealer likely charged the ...
No magical devices to bring a battery back to life.... except water if the level in low.
Based on my experiences with dealers, a crooked service tech told her a good battery needed to be replaced. During the visits later on, you got an honest tech.