According to the Naruto fandom, Rin did ask Kakashi to kill her in order to save Konoha, her village. After a three-tailed beast was put inside her, Rin decided she didn't want the beast to take control over her and destroy her home. However, she wasn't able to take her own life and Kakashi didn't want to, either.

What happened to the 3 tails after Rin died?

Since Rin died without having Isobu extracted, Isobu is the first known tailed beast to have "died" and revived. In the Three-Tails' Appearance, Isobu's capture took place much later than in the manga, but played out in much the same way.

How old was Rin when she died Naruto?

If you mean the current timeline, obviously Rin is dead, but Kakashi was 26-27 years old in part 1, and 29-31 years old in part 2, same for Obito. This will automatically make Rin 29-31 years as well, if she was still alive.