1) Verse to prostrate (sajdah verse), do we have any option not to prostrate while reading or listening to it?

2) Since I am living among sunni community while praying congregation at mosque, sometime the Imam recite sajdah verse but he just goes to ruku after that and continues to pray not prostrate. Should I follow the Imam or should I perform sajdah and restart my prayer?

3) I’ve read from some sunni article reading or listening to sajdah verse is recommended to do prostration, is it true?

1) It should be immediately after reciting or hearing.

2) If you can do it in a way that does not disrupt the congregation then you should prostrate and restart your prayers. Otherwise normally it is not allowed to delay, obligatory prostration, however, in such circumstances, it might be OK.

3) There are four places that it is obligatory to prostrate, and the rest are recommended. https://duas.org/Misc/sajdadua.htm