Yes, it is partly based on a true story. The creator, Carter Bays, has said that some elements of the show were inspired by his own life experiences and those of his friends. For example, the idea of a group of friends in New York City having various relationships and adventures is something that many people can relate to from real life.
There were also Barney's stories which were more about his wild escapades in the dating world. These stories, while not the traditional 'bedtime' type, were still stories told within the HIMYM universe. According to IMDB, fans often found these stories to be both entertaining and revealing about Barney's character. For example, his stories about the 'Playbook' were like these wild bedtime stories for the viewers, full of crazy stunts and pick - up lines.
The fanfiction of How I Met Your Mother can be quite diverse. Some offer unique perspectives and expand on the show's universe in exciting ways. However, there are also those that feel forced or don't stay true to the show's tone.
It's quite distinct. The characters and their experiences are new and unique. The settings and plotlines are also fresh and not directly related to the original show.
Definitely not. It's a fictional comedy series that's created for entertainment purposes. The plot and events are purely imaginative and not based on real-life events or people.