[Android General] Tzul:
How do you get TWRP installed in the first place? Sure, you can try to obtain root in Android with some questionable one-click-root tool, and then use an app like Flashify or Rashr to install TWRP. But this is kind of backwards. The traditional way is to first install a custom recovery, and then use it to install root.

You might be able to install a recovery via Fastboot, but that appears to be blocked more often than not. But you can pretty much always install it via SPFT.

Also, what if you "bricked" your device? TWRP won't do you any good if it doesn't boot, but with the SPFT you might be able to "unbrick" the device.

TWRP isn't discouraged at all. It's great for making backups, particularly of the large userdata partition.

You partly answered that question yourself. You can use SPFT at any time, even on a "virgin" tablet that is still running the stock recovery. Well, as long as you have a scatter file for your device, but if you don't and can't find one online, it's not too difficult to create one yourself (this guide uses an obsolete scatter format, but the idea of extracting all partition data from the SPFT's log files is still applicable).

You can only use TWRP if somebody has built or ported it for the device in question. And even then, TWRP might be configured badly and not show all partitions for backup/restore. With TWRP, you normally can't save the preloader, for example (not that it's important for most people). But with the SPFT you can create a truly complete backup, including "hidden" partitions.

For details about the partitions, read this.

You can ask the same question about the partition selection in TWRP's backup/restore. Select everything that is important to you. An initial full backup, before you even boot up the device for the first time, is always a good idea.

Here's how you use the SPFT. Enable the new "ShowByScatter" feature to automatically have the partitions show on the readback page. It does not show the userdata partition (your apps and data) by default, so if you want to make a backup of that, too, you'll have to manually add a new region. The values for this tablet's userdata partition are: start address 0x8f800000 and length 0x313580000 (for 16 GB tablets) or length 0x6b7380000 (for 32 GB tablets). But I recommend using TWRP for userdata. Because SPFT creates a partition image, which is always full size, even if the partition is as good as empty. TWRP on the other hand archives the actual files within the userdata partition, and therefore creates smaller backups.

They have some overlapping functionality, but don't really do the same. They are different tools for different jobs. SPFT is for reading and writing partitions, without having to boot up the tablet. It cannot access individual files, or install OTA/update zip files. TWRP is a custom recovery, it can read and write partitions, but also individual files. It also has ADB and USB support, and other useful stuff. But as explained above, you do not always have a working TWRP for each device...

No. Firmware updates come in three types:

SPFT archives (yes, some vendors distribute firmwares this way) - contain a scatter file and image files for all "normal" partitions

Type 0 OTA updates: contain mainly patches rather than complete files, and therefore can only be applied to one specific firmware version. The update basically increments the firmware from one version to the next, and only contains the differences between them.

Type 1 OTA updates: contain a complete Android system partition image, and a few others (boot, maybe trustzone, etc.), and therefore can be applied to all firmware versions.

A type 0 update is absolutely useless for the SPFT. But you can extract/convert the partition images from a type 1 update and flash them with the SPFT. OTA updates are of course intended to be installed by the recovery. Installation by stock recovery should always work - as long as the system partition was not modified. Installation by custom recovery such as TWRP can work, but might require some adjustments to the updater-script file contained in each OTA update zip file. That script contains a list of commands that are executed on installation, and it often contains integrity checks that will abort the update process if some system files are missing or have been changed (even if those files are unimportant).