Google recently released marshmallow 6.0 version for both android one and Nexus device and now google release it Android 6.0.1 marshmallow update for android one device to fix some minor bugs in android marshmallow 6.0.So you are running on android marshmallow 6.0 on your second gen android one device MMB29K then you can install android marshmallow 6.0.1 update by downloading it from the link given below.
List of devices with known comparability
1.Cherry Mobile One G1 (Philippines)
2.General Mobile 4G (Turkey)
3.I-Mobile IQ II (Thailand)
#Requirements
1.Your device must have custom recovery (TWRP/Philz)
2.Your device must be 60% charged
3.Make sure to do backup of your current rom.
#How to install marshmallow 6.0.1 in 2nd gen Android one devices.
1.Download Android marshmallow 6.0.1 rom .zip file from the link given below in download section.
2.Now paste the file in your device memory and reboot your device in too recovery.
3.After rebooting to recovery flash rom from it.
4.Clear cache,Data and Factory reset your device
5.Now reboot your device done!
6.Enjoys Android marshmallow 6.0.1 in your second gen Android One devices.