HTC Desire 816: How to Downgrade from MM to Lollipop or revert to full stock?

(bootloader) version: 0.5
(bootloader) version-bootloader:
(bootloader) version-baseband: 1.101.111011.20.0123
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main:
(bootloader) version-misc: PVT SHIP S-ON
(bootloader) serialno: SH47JWW07413
(bootloader) imei: 3527050655*****
(bootloader) imei2: Not Support
(bootloader) meid: 00000000000000
(bootloader) product: a5_ul
(bootloader) platform: hTCBmsm8226
(bootloader) modelid: 0P9C23000
(bootloader) cidnum: HTC__039
(bootloader) battery-status: good
(bootloader) battery-voltage: 0mV
(bootloader) partition-layout: Generic
(bootloader) security: on
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: 09813c97
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0

Can someone help me? I want to revert back to full stock phone. My HTC Desire 816 is rooted and TWRP installed. But I want a full stock phone again. Please help. I dont know also why my main is blank only.