If you getting error of Your System is Upto Date then follow below steps to Update your Canvas A1 running on LMY48M firmware with stock recovery.Note that your device must be unrooted and running on Stock Recovery.Here in this Steps by step tutorial of how to install the Android 6 OTA update on Canvas A1 manually.
#Update Micromax Canvas A1 to Android 6.0 Marshmallow.
1.Download the OTA file Micromax Canvas A1 from here and save the file on your desktop.
2.Now copy this OTA file into your Root of SD Card.
3.Then restart your device into Recovery mode.You can do it by Switching OFF your device and then pressing Volume down Key and power key for few sec Unitll you see the bootloader.
4.From bootloader select Apply Update from Sd Card.Then Select the downloaded file which we pasted earlier from the SD Card.
5.Now Wait till the file is flashed (It takes about 5 – 7 minutes to complete the process).
6.After it’s done select “Reboot to a system now”.
Now your Canvas A1 will reboot and first boot take Some time.After boot completes You have Android 6.0 Marshmallow on your Canvas A1.Enjoys!