I'd be surprised if the 3.5 ani event is actually a Monaka event because that means we would have (three) 30G events in a single year. It would also mean that both the 3rd ani and 3.5 ani event this year was 30G. Not to mention Monaka getting another SS style this soon is quite early. It's definitely possible, but it just seems unlikely.

Imo the sprite update might be used for a snap event or more likely, a bond episode for Unison Kura. Meanwhile the 3.5 ani event will be for Ruka. If we go by past trends, the 0.5 ani event was for chapter 2, the 1.5 ani event was for chapter 3, and the 2.5 ani event for was 4.2. Sequentially it would only make sense that 3.5 will be about 5.1.

This is my schizo timeline
>7/10
3rd ani Carole & Vritika / 3rd ani Aoi gacha
Vritika got a sprite update too so she might be getting her SS3, but it could also just be for 3rd ani Carole's bond event

>7/17
The special stream guest is Kura's VA to promote Unison Kura before anniversary. We might get a snap event too, but most likely not when the exchange for the current event ends on 8/3

>7/24
They'll rerun some limited gacha. Maybe Unison Ruka or buff rider Nanami

>8/3
3rd ani Ruka and Tama for the 3.5 ani event. 3rd ani Aoi might appear here too if they want to delay Tama again

>8/21 (end of 3.5 anniversary and 3rd ani styles)
3rd ani Aoi and Byakko. Though this could completely be swapped with the gacha on 7/10 if they want to follow up the 31B event with Aoi and Byakko, which does make sense.