If you have played the original Digimon World DS then you will feel intimately familiar with this game.
The scope of the game is much larger then the original. You can obtain more digimon and you now also have the ability to DNA digivolve them.
Still, unless you know a fusion it is sort of difficult to actually get a new digimon this way. Good thing it tells you what the outcome is before you make it irreversable. :)
Farms I believe are more or less the same, Digimon of the proper species and personality may give you Quest Missions when on the farm. You can outfit a farm with Food, Defense, Species Exp, and Attribute equipment along with a BGM and a layout. The latter two, BGMs and layouts, are specific to the farm you buy them for unlike farm goods which can be placed and taken out of one farm or another. Ech farm has a capacity to how many digimon and goods it can hold with higher ranking goods taking up more space.
Battles are carried out EXACTLY like in Digimon World DS, There are Five Zones and you can only have three digimon in your active party. I believe now though you can also bring three digimon with you for back-up. These digimon can be switched out in or out of battle and get full experience also.
Overall, this is a very colorful game yet it is hard not to say it does not feel familiar to last years Digimon World DS. In the end, play what you like and have fun.
I hope this is suffiecent information for the would be buyer, if you need more, you need only contact me. If you also wish for my code..ask.