Hi, I tried few battles but I'm still not clear who comes next and why. In the first battle I got stuck at the start because I tried to make the game faster but didn't realize that I need to hit the button on the right to start - I would say highlight what is player expected to do next is better than tooltip help beforehand.
For you questions:
1. I stopped because I didn't care enough for the plant icons. If they would have more character they might be more likable.
2. Not really, I would try to explain to the player what is going on when it's happening in the first round so the player can adapt. One option at the time.
3. Yes I got that after first round but it felt like work trying to figure out what is the best strategy.
In my opinion, in this genre like plants vs zombies it's very dependent on the graphics. You have to fall in love with the characters and be curious what each offers. Only then you will try to explore all possibilities of the game.
Good luck with improvements!