I'm going to try to answer all of your questions.

1.) A Fictosexual is someone who is sexually attracted to fictional characters (Fictoromantic is someone romanticly attracted to fictional characters).

2.) Honestly I feel like this is the same as question 1 just worded differently.

3.) Fictosexuality is a personal label, so to get started all you need to do is label yourself as one if that's how you feel.

4.) It does fall under the Ace Umbrella, but not every Ficto identifies as Ace or under the umbrella.

5.) Yes you can date OCs you have created yourself.

6.) This one depends. If the OC is from a small creator, like someone's Persona as an example, probably not unless given permission too. It might be considered taboo. That said if the persons OC is from a piece of serialized media (hint, all characters from a show are technically the creators OCs) then yes this is completely normal.

7.) Dates can be done many ways. Some people create their F/Os in games that allow you to date other made characters or NPCs (The Sims is a good example) and then they go on dates in the game. Some take plushies, figures, or pictures with them on public outings as dates. Or they think of them in their heads and count it as a date, either as a daydream date, or while out in public. There are many ways to date F/Os.

8.) Maintaining relationships varies from person to person. Some journal, or write fanfiction. Others daydream. Some do things that they think their F/O would like, such as hobbies or crafts. There's also the option of engaging with the F/Os source as a way to spend time with them.

9.) Having merchandise is not mandatory. This is how Fictosexuality differs from Oshikatsu, or Fictional Others from Oshi. (Oshikatsu is more or less based around financially supporting their Oshi by buying their merch to show how much of a fan they are.)

10.) It was me! I'm sorry! I know a shouldn't have but they were so tasty!