No, Boruto is alive in the manga. The plot hasn't led to his death. However, the manga is ongoing, and anything could happen in the later developments.
The story of Black Ops 3 is somewhat related to Black Ops 2. Some storylines and events carry over or have references that link the two. But it's not a direct continuation; there are new elements and developments too.
The story of Black Ops 4 is separate from Black Ops 3. They have different settings, characters, and plotlines. Although they belong to the same franchise, the narratives are independent of each other.
Yes, Boruto is indeed a manga. It expands on the Naruto universe and offers fresh perspectives and storylines. Many fans enjoy reading it to delve deeper into the world created by the series.
Naruto would be devastated. He might blame himself for not being able to protect his son. Sasuke would be angry and would likely go on a hunt for the perpetrator. His friends like Sarada and Mitsuki would be heartbroken. Sarada might vow to become stronger to prevent such a tragedy from happening again.
As of now, no. In the Boruto series, their relationship is mainly focused on their friendship and comradeship as ninja. There are some moments that fans might interpret as having a hint of something more, but the story has not made their relationship a romantic one in an official capacity.
No. The official Boruto series is focused on the growth of Boruto, his friends, and the new generation in the ninja world. Fanfics are often creative interpretations by fans, but this one sounds like it's not in the spirit of the official series at all. It's likely a non - official and inappropriate creation that has no place in the official Boruto story.