In most cases, no. American fiction is focused on the main narrative and doesn't commonly incorporate post-credit scenes. However, there might be some rare exceptions in experimental or unconventional works.
It can be quite important. It might set up future plotlines or introduce new characters. For instance, it could be the start of a new arc for a character like Qi'ra.
Yes, Shang Chi is from comic books. His stories have captured the imagination of fans. The comic versions provide in-depth backstories and plotlines that add to the depth of the character.
In the comics, Shang Chi has no established gay identity. The focus of his storylines lies elsewhere, mainly on his martial arts skills and adventures.
No, Shang-Chi is not depicted as gay in the comics. His character's romantic and personal relationships are typically presented in a heterosexual context.