Is there any specific requirement or limit to anything to be a moderator? (e.g. minimum reputation score) And also, what are the duties of a moderator? If possible, a full list of duties would've been perfect.
The thing about Stack Exchange sites like Arqade is that they are mostly community-moderated. As you ask and answer questions, you accrue reputation points. At certain reputation tiers, you unlock different privileges.
Some of these privilege levels remove restrictions around commenting, editing, and creating tags, and others allow you access to more serious tools, like voting to close/reopen other people's questions, and later, even voting to delete or undelete them.
So, by continuing to participate normally, you will actually get access to most of the moderation toolset over time.
Is there any specific requirement or limit to anything to be a moderator?
Mods (those with diamonds next to their names) are elected by the community. Elections are held when the current mods feel like they need a hand with the workload, or if many mods step down at once.
Requirements are listed on the election pages. The only hard requirement for nominating yourself is 300 reputation, but generally speaking, if you want other people to vote for you, should show a history of positive interactions with the site and it's community (e.g. participation in flagging, reviews, chat and meta), and be an active member of this community.
What are the duties of a moderator?
Moderators are considered 'exception handlers' - we're mostly here to guide the community, help out, and override when necessary. Most of what is said on the Help Center Article about moderators is accurate. It's hard to give a 'full list' of duties, but to give some common examples:
- Continue to be present/active in the community
- Handle flags & the occasional spam
- Clean up comments under posts & move ongoing discussions to chat or meta
- Help to organise the community, and guide discussions on policy or changes to the site
- Stop arguments, protect/lock questions and deal with warnings/suspensions for problematic users
- Cut through red tape for community-led efforts (like renaming tags).
Generally speaking, if you are looking to become a diamond moderator, the best advice I can give you is to be active. Ask and answer questions, participate in chat and/or here on meta, and later, when you get access to them, participate in site tasks such as reviews. If you are invested in the site, and a genuine and positive person, this will reflect well when an election does run and you nominate yourself.