Depends on the other IMs, but as far as I know, at least Signal and WhatsApp have no keys they can give the government. WhatsApp could potentially sneak a backdoor in their closed-source code, but I don't think that's something they'd have incentive enough to do.
What does that even mean? Every ISP has it's own filtering system, some (or maybe even most of them) are custom built ones. There is no such thing as single government approved DPI.
That’s right, but basically dpi sends tcp reset in case of https or 302 redirect in case of http before target server response, since it’s located nearer. There’s a tool to bypass this, so you can read more there. https://github.com/ValdikSS/GoodbyeDPI
Maybe they just don't have enough balls to go after the biggest ones (WhatsApp and Viber). Plus, other IMs don't have public channels anyone can subscribe to. IIRC that was the original problem, "extremist" channels. Why did they ask for encryption keys instead of blocking channels? Who knows lol.
Telegram still works without (manually adding) proxies :D
EC2 Ireland (at least the subnets where my servers are) also works.
Also could someone from Russia confirm telegram/AWS are blocked?