Download Android ICS 4.0.4 Stock Firmware for Lenovo IdeaTab A2105 tablet from here or here. Download another Lenovo firmware from here.
Archive name: Lenovo_A2105_4.0.4_20160925
Archive file size: 244 MB
Model: Lenovo IdeaTab A2105 tablet
Build number: msm7627a-user 4.0.4 IMM76D 0000476 release-keys
Platform: Qualcomm Snapdragon MSM7627A
Caution: Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.