First Exploration Quest 1900, Day 3 of Playing

After level 10, ads pop up every two completed rounds, and sometimes mid-game. If you want to skip ads, try exiting the game, going to Playo, and pressing 'Start'. It should skip the ad. I've completed two hidden quests while doing exploration quests, and there are about 8 hidden quests in total. There are two payment-related hidden quests: 'App Purchase' and 'Purchase over 11,000 won'.