Emojis are standardized exactly the same way as text is, both are defined by the unicode standard. They might not be rendered uniformly, the same way that text rendering depends on the font.

If this isn't satire, that's literally what Unicode and UTF-8 are

I thought Emojis were a set standard but how they're rendered can change. So whatever it is that identifies the heart emoji is universal but iPhone, Samsung, Google, etc might render that heart differently.

Although I agree it is risky, emoji are unicode characters, just like any other unicode character. If, and that's a big if, the programmers do their job right, it shouldn't matter if you use an emoji or a random kanji. It's all just another character. That said, I don't trust programmers enough to run the risk. Your password might work fine on the website but then fail on the mobile app.

Someone else said "good luck on the desktop", but Windows actually has an emoji picker built right in. Win+. will bring it up. Another fun fact, usernames and computer names both support the full unicode set on Windows, including emoji. Some fun can be had with that knowledge. I haven't tried it on Linux or MacOS yet.

Yes there is, . I would say most modern devices/systems utilize it too. The reason they may look different from device to device is because the presentation style can be modified by vendors, somewhat similar to using different fonts to make letters look styled.