First of all, the mobs are not easy, so best go 20 30 lvl's below ur lvl at first, in case u are not very strong, see how it goes, then go high as ur troops allow u to.
Drops as far as consumables go are similar, different are the equips that can drop and the lvl of the core.
1. Here is where u find the feature
2. This is what u see there, move the mouse on the writing so u see the lvl
3.Pick a lvl and this is what u find, mobs randomly siting in squares
6.Using shovels, these u can use anywhere, yet if u have a 2 or 3 on map (number of chests surrounding the number, maybe best u dig there)
7.Using detector, u can risk and go somewhere that u have no numbers, it's all about luck.
8. Only difference between advanced key andnormal is the score u get: 10 - normal ; 30 - advanced, the drop from chest is same
If u are not yet strong enough to fight, but u are lvl 100+, enter the feature and use ur dig and ur detector randomly on the map, maybe u find some chests, u can move around anywhere in first map. U can try ur luck like this till u get stronger.