Snapback, connect&die and squeeze are 3 of the most important techniques to think about while trying to get creative about a position. If you start out with connect&die in mind, it’ll be easier to detect it.
Also, you can think about liberties. When you throw in, white will have to take for sure - that is just one step reading. When they take, seeing that they will be taking their own liberty (cuz they’ll be touching your stone, t5 - t4) might be worth noting. They will also be making an empty triangle, which is usually inefficient shape in terms of liberties. Seeing the throw-in results in an empty triangle that takes away its own liberty in the very next move could make it easier to settle on the throw-in when browsing the position initially.
So, my thinking was B S5, to which W responds with S4 and says “wrong”. But B T4 would be my next move. Why is it wrong? AI suggests S4, which OK, but don’t I kill everything anyway?
Ko recognition and assessment can become better simply by playing them in your games. Just a matter of cumulated experience. It’s something not very natural at first but if your games miss kos you can even create some, no joke! Think on it when attacked, and you feel to move too slowly to escape.
Enjoy kos as much as cutting or killing or pressing…
I’m not sure I understand the goal in this…
I can’t kill, or get two eyes.
I saw the solution, but I don’t see how the ending position works for me.
Or maybe I’m rusty.
In terms of what to aim for I can give some ideas of expectations, but there’s spoilers below. I know you know the solution, but there’s maybe one extra variation including (assuming I’m reading it right )
The idea is to exploit the shape and shortage of liberties. I’ll assume I’ve gotten the first move correct a and b look like key moves but the order seems to be important.
So with 1 it aims to connect the black stones to the outside on the first line. If white knows what happens if they resist, or they just capture the stone instinctively black can connect on the first line. White can’t play the X because it’s self Atari, and being close to corner means it takes white an extra move to start filling liberties from the far side (they can’t play in the corner immediately.)
details within details
Even if white tries a throw in type trick I think they’re just a move behind
If white tries to stop it Black can save the stone in Atari, and white doesn’t have enough liberties to Atari/capture because the corner is so close. T12 will be Atari for black next move.
But tbh I need the practice. 
