Is there something specific you need to do to get the "no" gear in the water temple? I've only gotten the trousers and shoes but the top and hat don't appear at all.
They can all be found in the chests on the third floor. Each room gives you one specific piece, so just savescum in front of each chest. There is no head piece, but there is a hand piece you're also missing. For more info, you can check the walkthrough
It's in the third room of the second level of the Deep Mines. You can check the walkthrough for more details. 
0.21.1 is the most recent public version of the game. If you're playing that, you've already reached the end with Richtor's fight. If you wanna support Spedumon on Patreon, the latest version there is 0.81 (the Patreon version has a different numbering system than the public version, it's not 60 versions behind). Otherwise you gotta wait til November for the next public update.
In order to keep your save files, you must copy the entire "save" folder within your current game's folder (which is inside the "www" folder), and use that to replace the one in the updated version.
You need to finish each repeatable Quest Guild quest in Piratetown at least once (all nine of them, you'll need the golden badge for the 3-star quests). Then Buba will ask you to talk to Vulfox in the guild lounge. You can check the walkthrough for more details. Sword is the leader of the royal knights you met in Safen at the beginning of the game. So far, there's no use for the key yet, both in the public and the Patreon version.
Not sure what you mean by "characters list", but there is a walkthrough. Scroll down, and you'll also find links to all the different items in the game.
After you hand him the guestbook, he appears in Bangers Club in Gloomy Forest, then at the beach. You need to tell him he's gay every time. After the third encounter, there's a random chance for him to appear in the Shiptown harbor restroom. Just leave and re-enter until there's a pink "4" over the right stall, then enter the one in the middle. After you boned him there, you can find him in the final call in the Pine Island prison. After watching the event there, talk to him again upstairs to finish the quest.
1. Finish each repeatable Quest Guild quest in Piratetown at least once (all 9 of them), then talk to Buba, he's gonna tell you to go see Vulfox in the guild lounge.
2. After you spent a night at the Paradino hotel, talk to the bear at the pool outside.
3. Finish each repeatable Quest Guild quest in Paradino at least once (all 9 of them), then talk to Rexardo in the guild lounge.
If you got any more questions, check out the walkthrough.
There might be a bug with the buff.
Edit: Looks like it only works with Swords for now, I've found a fix for it, but it requires a whole new build to be made, so the fix for it is coming in the 0.24 version the latest, if there won't be any major bugs to fix! It's been added to the bug list here:
https://itch.io/t/5495969/bugs-of-build-023
After you show him the guestbook, he's in the Bangers club (Gloomy Forest), then at the beach, then there's a random chance for him to appear in the Shiptown harbor restrooms (keep re-entering until there's a pink "4" over the stall door). After that, you can meet him in one of the prison cells on Pine Island. If you got more questions like this, check out the walkthrough.
Did you already do the previous steps? Aka handed him the guestbook in Safen, then called him gay at Bangers in Gloomy Forest and at the beach? If so, you just have to enter and re-enter the restrooms until there's a pink "4" over the stall door, so you know he's in there. It might take a few attempts, depending on your luck.
Fire Dungeon, second floor. In the room with the last fire guard before you reach Duiro, head left and follow the hallway to the jail cell with Wizzy in it. For more questions like this, check the walkthrough.
Yes, all three are on the island. There is a walkthrough, if you wanna know where precisely.
If you still got access to your old computer, you can just import the "save"-folder from your game. The path is Small On Top[VERSION]/Small On Top/www/save. You'll need the entire "save"-folder, just put it on a USB stick, and replace the "save"-folder on your new computer with the old one. However, depending on how old your save files are, they may or may not work with the latest version of the game.
How do I get this event?
Where Cal's Cafe attic help
