The old tree system was much better, it allowed you to mix exercises from different topics. The new path system locks you into one topic until you know all the sentences by rote.
The main objective is not to complete lessons, but to learn. If you use up all your hearts because you make too many mistakes you're obviously not learning. At that point Duolingo completely fails though, instead of telling you to go back and practice, it asks if you want to buy hearts with in-game currency or switch to the paid super max hyper ultra AI whatever it's now called for unlimited hearts. Unlimited hearts doesn't give you shit though, it allows you to bruteforce your way through the lessons to get XP to rank up in the completely optional leaderboards, it doesn't help you learn. It's only pay to win if you see it as a game and not as a language learning app.
Well, the ending of the third book changed a lof in the world. A sequel could be interesting, but unless everything goes to shit the world would go to something we could consider normal, a world without the hunger games. This mostly leaves prequels, so far they were all tied in some way to the hunger games, but there are more prequel options like something during the first revolution.
Yeah, that was an interesting bit, how they replaced her. Same with the reaping escalating and one of the tributes getting killed. But the general plot follows the first book very closely, I suppose that's to be expected as the games are more or less always the same, just with a different arena.
It's technically not countries participating, but broadcasters and they need to be independent of state control. The russian broadcasters were not kicked out for the russian invasion of Ukraine, but for being state controlled. They were accused of this for a long time and the invasion was the final straw.
Why do you assume that OP only has/had male friends?