On paper, the Hyundai Ioniq 5 with a full battery shows a range of around 500 km, but that's under ideal conditions! In reality, especially in summer heat with the AC on, the battery loses like 20-30 percent right away! Plus if you're hauling heavy luggage and get stuck in Moscow traffic with constant stops, energy consumption shoots up even more. Driving style matters too - if you cruise calmly at 90-100 km/h, you'll get decent economy, but if you floor it and constantly accelerate, the range just shrinks in a really depressing way!
For an 800 km round trip, I wouldn't risk doing it on a single charge! Honestly, it's better to plan at least one pit stop halfway - somewhere around Vladimir or Nizhny Novgorod. The charging network is pretty decent there now, and you stop for 20-30 minutes - you get a break, the car charges up! Psychologically it's way more chill, seriously!
Here's my advice: punch the route into your GPS with charging stops in mind, check where stations are along the highway to Kazan, and plan your stop ahead of time! It'll take longer than a gas station stop, but you'll get there stress-free and without the risk of getting stranded in the middle of the highway with a dead battery!