The Rock challange is nearly impossible to beat, you must have a good RNG of the brown rocks, the best I goted here was 14/15 with 2 sec left for the 15 rock wich was impossible to get, the archer one is a bit of rng as well, since you can get like 1 archer spawned then nothing for like 20 sec, then 3-4 archers just randomly come at you, as for the harvest I nearly goted it you go 8X2 arround watering once and moving on in a so called "circle", the problem I goted here was, when I water the last crop the timer goes to 0 I get the gold win and at the 0 the 15/16 grown turns to 16/16, cause the animations take a bit, so yeah a bit buggy :S