Oliver the Vocaloid does not have an official last name.
You need to purchase it from the official website.
Definitely Miku. People who have no idea what Vocaloid is would recognize Miku's official art or the chibi of her with a leek.
As of my last update in October 2023, there hasn't been any official announcement regarding a Vocaloid concert in Ireland. Vocaloid concerts typically occur in larger cities or established venues, so it would depend on demand and logistics. For the latest updates, it's best to check official Vocaloid social media channels or websites.
Gackpoid does not have an official age and most VOCALOIDs don't.
Kaito Shion (Shion Kaito) is supposed to be a Vocaloid, but he is not an 'official' Vocaloid. He has blue hair, and seems to have a fondness for scarves. He adores ice-cream and it is his character item. He is supposedly very close to Meiko Sakine (Sakine Meiko) but unknown whether as good friends, or 'siblings'. He supposedly has a VOCALOID programme, but it is not released. He is often featured as Miku Hatsune's (Hatsune Miku) lover, and the pairing grew in popularity when the song 'Canterella' was released, featuring several different music videos telling the same story.
"VOCALOID" has no official anime or manga, as well as no official story, so the answer to your question is no. VOCALOID is a program in either Japanese or English in which users can create or change songs. However, there is an unofficial manga called "Hatsune Miku: Unofficial Hatsune Mix." Though it's an unofficial book, it has still obtained a lot of respect as a funny manga. There are also quite a few vocaloid guide books on how to use the program. You just have to keep searching.
Not officially, no. VOCALOID is a synthesizer program that allows a user to create vocals for a song without hiring a vocalist or getting a real vocalist for a song. The Vocaloid franchise has many different software, and each one has a mascot for the particular type. This is to put a face/image to the voice, and therefore each mascot does not have a personality NOR is there an official pairing for the different mascots. For the sake of doujinshi or fan-based creations, the mascots may be paired with any one of the others, so KAITO may be in love with Miku in a user-created song, or KAITO may be in love with MEIKO in a manga. It is up to the person using the characters or the software.
Seungho and Mir.
Yes, Ai is a vocaloid. A vocaloid 3 to be exact.
Black*RockShooter
NONE, she doesn't have any last name.