Stand alones sell too and a great many books work better as a stand alone, imho.
Don't sweat this.
Just pitch your book. No sense in forcing a series if it wasn't meant to be one.

There are some agents who rep self pubbed works. I do not. For me, the best time to pitch me would have been before you self published. Do some research into agents, it's not a deal breaker for others.

I don't require social media from my clients & I have signed some who don't participate, but many publishers like to have authors who have one.
I'd say MOST of my clients are on social media. It's not a deal breaker for me & I think the pubs who require it are outdated.

That the writer doesn't send a synopsis, but another pitch paragraph.
I want beginning, middle, and END, spoilers and all.

I'd let them know.
They may pass for the very reasons you've just fixed in the revision.

First pass = read query letter. Reject or goes to 'Maybe' pile.
Second pass = read synopsis. Reject or goes to 'To Read' pile.
Third pass = read sample pages. Rejected or requested.

I say go for it. Those who don't want responses have likely disabled the "reply" function on queries.

I'm very non-sporty, so I'm not the agent for that manuscript. However, I've seen editors specifically request sporty manuscripts, so there's a market for it.

Depends on the agent. For me, I can be heavily editorial to, "This is perfect, let's go to submissions," depending on the state of the manuscript.

Pitch it as a YA crossover.
Problem solved.
xo

I can't speak to this, b/c I legit have no idea.
There are A LOT of pitch events and agents can and do burn out on them, but I also know some agents who close to queries and ONLY look for stuff via pitch events, so I say, DO BOTH = query and pitch events

Nope, not mandatory.
Although some publishers looooooove those angsty YA voices.

Bashing other books is a big no no.
Flirting, also a no no.
Categorizing a book incorrectly b/c my QM doesn't have it listed - there's a reason why. That's a no no.

Personally, darker material w/ depression is not my fave as I find it a difficult read. I don't enjoy being sad, and tough subject matters have to be handled with hope or I'm not interested.
Series=good
Pineapple= sure, why not?

1) Depends on the categories/genre. If it's Erotica Romance & Picture Books, then YES I highly recommend 2 diff pen names. If it's Adult Thriller & SF, then use the same.
2) I'd recommend you sub an agent who reps both FIRST. If nothing pops, then try with your strongest cat/gen

I always sign my client for their career and I THINK most do the same - with a few exceptions. Doesn't annoy me how long it takes to write a book. Everyone's process is different. It takes however long it's going to take. No use rushing and delivering subpar work.

1. I wish I saw more Latinx anything. But if we're being general, I'm not seeing a lot of YA Thrillers lately. Would love to see more of those...
2. Brie.

You could. But I don't think you have to. I would just say "I previously queried MANUSCRIPT and loved your feedback and thought you would be interested in MANUSCRIPT 2."

When people say "this is the only book of its kind" or "this is the best book you will ever read."

Anytime either of those things has been said, they were very untrue.

Yep!