Basicly yes.You have to do nothing , but leave the app on...That "randomly" also is related on how the results of the benchmark will be , let's say that the more "powerfull" your phone is the more coins you will get.
Also you can play games to gain a few more coins.
As for the ads, i really hope that they will keep it as clear as possible...if it annoys people, it would really be harmfull to the project. I hope there will be as few as possible, or none.......

So, I just visited the Electroneum website, and it's official: Token Sale Has Closed Early. Per the developers: "The token sale has reached the $40M hard cap, thanks to everyone who has purchased Electroneum. There will be an updated on social media shortly."

Total # of registered users: 290,827
Total Electroneum Sold: 4,408,781,842
Total ETH Raised: 42,076.8847
Total BTC Raised: 4,878.1358

So, I just visited the Electroneum website, and it's official: Token Sale Has Closed Early. Per the developers: "The token sale has reached the $40M hard cap, thanks to everyone who has purchased Electroneum. There will be an updated on social media shortly."

Total # of registered users: 290,827
Total Electroneum Sold: 4,408,781,842
Total ETH Raised: 42,076.8847
Total BTC Raised: 4,878.1358

Now that the hard cap has been reached, is there any chance of an earlier blockchain (&miner) activation or are you bound by the given date ?