[Q] Steps for backuping, modding and eventually restoring

Hi all,
I want to mod my stock M8 and I would want to make each step correctly.
First of all, my M8 has this property:

Code:

---

(bootloader) version: 0.5
(bootloader) version-bootloader: 3.19.0.0000
(bootloader) version-baseband: 1.22.21331147A1.29G
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main: 3.31.901.9
(bootloader) version-misc: PVT SHIP S-ON
(bootloader) imei2: Not Support
(bootloader) meid: 00000000000000
(bootloader) product: m8_ul
(bootloader) platform: hTCBmsm8974
(bootloader) modelid: 0P6B10000
(bootloader) cidnum: TIM__401
(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: 2e9b7c51
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0

(this is info in recovery mode... )
*** Software status: Official ***
*** Locked ***
M8_UL PVT SHIP S-ON
HBOOT-3.19.0.0000
RADIO-1.22.21331147A1.29G
OpenDSP-V46.2.2-00564-M8974_FO.0811
OS-3.31.901.9
eMMC-boot 2048MB

---

Backup:
I have 2.22.901.5_firmware.zip, 2.22.901.5_recovery.img and 3.31.901.9_ckpv5.zip files. Are they useful backup for returning stock?
I will use also Helium to backup application, and I will backup all my files on a cloud.

Mod:
Which are the steps (and relative howTo) for modding the M8?
Install bootloader, recovery, root, going s-off, install rom...

Restore:
For returning S-ON, I have to buy a Sunshine License, right?
For restore a nandroid backup? What could I do?

Thank you in advance,
Fed10