Samsung Galaxy S4 Mini is the younger sibling of the Galaxy S4. It runs on a 1.7GHz dual core Snapdragon processor, with 1.5GB RAM and 8GB internal storage (16GB in some regions). The 4.3″ Super AMOLED display has a resolution of 540×960. The S4 Mini runs on Samsung Touchwiz and comes with the standard suite of Samsung apps.
Samsung will not send out the official Marshmallow update for Galaxy S4 Mini or any of its variants. But there is a CM 13 ROM available for 3G variant of Galaxy S4 Mini which will update the device to Android 6.0. If you want to install the ROM, a detailed guide is given below.