New player, help with a build idea please ^_^

Hi y'all. I'm a fairly new player, just got wrath of the righteous (hope I'm in the right place 😅) I've played a few games in the past like this, not a ton though. I was hoping to get a little help. I don't currently have the dlc, but considering it if that changes anything.

So I know going for an extreme multiclass is.. a bold choice, but I'm not playing on hard and from what I read I think this could be viable enough. Plus it sounds like it would be pretty fun(ny) 😊

So I was thinking a pyro gnome arcane rider.. riding a racer velociraptor.. with arcane trickster 😅

So I had a few questions, and was wondering if people had thoughts. I'm totally open to ideas changing things up. Started off with this just looking at arcane trickster, and it kinda got away from me, so many choices lol. I'd like to stick with a gnome/halfling riding a velociraptor, so fun build ideas in that direction would be appreciated 😊

I was thinking of going trickster -> legend mythic, 20 in arcane rider and 10 in arcane trickster, leaving me 10 levels leftover, with 1 of those needing to be something to get my raptor

So the first thing I was wondering, though I think I found someone with an answer saying yes, was:

1. If I didn't want to dip into a sneak attack class, or at least not right away, I can use the sneak attack dice from the trickster mythic/accomplished sneak attacker(feat) as the prereq for arcane trickster, right?

I don't know how strongly I want to lean into sneak attack. I'm open to dumping arcane trickster altogether, adding some sneak attack class levels, or just leave it at the lvl 10 arcane tricker plus the feat and maybe there's more ways to add sneak attack dice?

2. This is gonna be pretty important for the build. I'm confused on how animal companion leveling works exactly, I've seen contradictory answers. If I do start as say mad dog and pick raptor then switch to arcane rider, which doesn't have access to the velociraptor, would it still level up, or is arcane rider basically incompatible with the raptor unless I went say 20/20 or 16/20 with boon companion?

I saw a few other animal companion classes that peaked my interest at least, so it wouldn't be a total loss to not do arcane rider, but that still sounds like a blast. I'd probably just keep the horse until switching to the raptor would make it level 7 so I can ride it

So I was thinking, if that's all good, with the remaining 9 levels I could do some in a sneak attack class, mad dog, cavalier, or hunter, and could also use loremaster as filler

As a question 3: Would I get benefits from loremaster raising my caster level further? I read something that sounded like I could do that but I would need to use those prestige classes before level 20 and then proceed to get the rest of my caster levels from the "base" class after the prestige class ones. So if I were going to do loremaster, I'd want to plan it out ahead of time. However, I wasn't sure if loremaster would be a waste and I'd rather gain say rogue levels for more sneak attack, especially since I'd be losing at least most of my trickster mythic sneak attack benefits

Anyway, sorry for the long post, thanks in advance for any advice! 😁

Edit: Ok if the arcane rider/arcane trickster sounds just crazy enough to work, I guess I'd also be down to stick with the horse. At least then I could cast animal growth on it and that also frees up my race. Still.. gnome on a velociraptor 😆

Edit 2: Follow up topic I forgot about - 4: Does anyone know how spell combat/spellstrike interact with surprise spells? The curiosity is part of what kept me interested in multiclassing these in the first place. Any other ideas for cool interactions/combos with this build are very welcome 😊