Not even dual boot.
Just depending on the password/pattern entered, log in as a different user. It's possible to do in Android as an app. I've been meaning to write one, but it seems like lots of work and upkeep.
What you describe might be almost achievable using Android work mode, and an open source tool like Island - you can have a second instance of apps (like WhatsApp or signal or telegram) independent of the first instance, and you can turn work mode off if needed.
If your adversary knows about work mode though and checks if it's available, this won't help you much.
What about the people under 18 who I assume could take the poll and also people who didn't go to vote but took a few seconds to take the poll on Telegram?
Also what about all the babushkas who most likely voted for Lukashenko but don't have a smartphone?
This is not to say that more people didn't vote for the opposition than the official numbers state. But Lukashenko still could have won.
We'll say Belarus has 1m people that are old enough to both have a smart phone and be under the legal voting age (and that's being extremely gracious). Unless you're saying literally EVERY ONE OF THEM voted in this poll AND voted for the opposition, there are STILL more people of voting age in the telegram poll who voted for the opposition than "officially" voted for the opposition. The numbers are nearly impossible to believe unless Telegram is intentionally fudging the numbers.
There is lots of corruption and bureaucracy and lawsuit-avoidance driven construction. Right now the cost of constructing subway stations in NYC is the highest in the world.
It would be quite laborious to figure out "normal" user traffic patterns and then adjust to those. You would have to collect data on a bunch of users and then shape your own traffic to match.
Only makes sense if you are doing it for a bunch of people and at that point you are another VPN provider.
Regarding SMS interception, you can do it with every other messenger that uses this technique, which is basically every messenger that doesn't use passwords.
Regarding the nonce attack, it looks like the devs responded and said it was because of poor random numbers source on the client, which I personally don't understand as a justification. However, they said they'll remove it in the next update and that nonce has been "0" up until now.
Regardless, all of these messengers for cell phones aren't great if you are paranoid. That's because the hosting company's servers have all kinds of data on you as it is. Your contacts, access to SMS, access to location, camera, mic, photos, and all the files on the device.
This is true for all the messengers that are currently in widespread use.
The wikipedia page for it explains it well.