No. Pokemon is a family - friendly franchise that targets a wide range of ages, from kids to adults. Fanfics with 'lemon' (suggestive or adult content) are not acceptable in the official community, regardless of the sexual orientation aspect like 'gay' relationships being explored. It goes against the family - friendly and positive image of Pokemon.
It depends. If they don't violate copyright laws and are not for commercial purposes, they might be okay. But if they copy official content without permission, it's likely illegal.
There aren't any. The Pokemon world is focused on adventure and friendship, not such inappropriate content. Such comics would go against the nature and values of the Pokemon brand.
In the comics, Frenchie's sexuality wasn't explicitly stated as gay. It might be open to interpretation depending on how you read the character's storylines and interactions.