Thanks, was really excited to finish the whole process. Decided to have the game easy enough for me to finish the whole task.
I'm planning to do iOS as well yes, I just need to get my hands on some Apple gear, I don't think I can export on a PC.
I'm not using achievements in this game but I'm using 2 instances of leaderboards, one for each game mode. They seem to be working well. I hade some problems making them work in the beginning. Google seems to be really slow when caching. I did some changes and it could take a day or two to actually work. There are some expressions in C3 to catch the errors, I was using them to see what was going on.
My main problem was that all players only saw one entry in the high score, my score. I found out that the players need to enable their "Let others see your game activity" in their game setting, that way their score will be seen publicly. This setting is off by default.
Also, my leaderboards only worked after uploading the game to the Play store and in alpha mode, internal mode didn't work, not sure why. In the game services, you have to add all the players to a testing group and include them in the alpha/beta mode.
Basically, I just browsed every link I found in the play console and game services and made sure everything was linked together.. :)