The above question was originally closed, and now has four reopen votes (though in the review queue it has three votes to be left closed). There are two rather different comments under it:
Each question here should be a single question, and an artefact here is that I think some of these questions are dupes of question already asked. [...]
The linked questions together provide answers to all parts of this question, but I voted to reopen, because a general and directed answer to the issue of "am I understanding this correctly" is exactly what we should answer in a single place on this stack.
For reference, the "linked questions" this refers to are the following (probably):
- Can a spell be prepared once and cast multiple times?
- How do I determine how many spell slots I have when multiclassing?
- If I multiclass into 2 or more spellcasting classes, how do I determine my known/prepared spells?
- I don't get the spell slot system for D&D 5e's Warlocks
- How does wizard & cleric spell preparation and casting work?
- How long do a spellcaster's prepared spells stay prepared?
- Can you have more spells known of a certain spell level than you have spell slots of that level?
- How does adding Spells Known and Spell Slots work?
- Do class spells take up spell slots?
Going back to the comment though, these are, of course, rather different. I personally feel the question should either be closed with various duplicate targets (one for each question it asks) or be closed as needing to be more focused (it asks multiple questions); however, I am just one person, and am not deadset on that being the only option here. What I don't want to do is to hammer-close the question and cause a close/reopen hammer war.
So I'm asking this here: Should this question be open or closed?