You were trying to use SS. If you would read, you would know that only 4.2.2 TW and GPE ROMs work with SS unless you have the latest SS, but then again no AOSP, AOSP, CM or MIUI will work. Since the new board is able to have a custom recovery because it is pre MF3, use that to flash those types of ROMs .the error 7 is because you tried to OTA update with a custom recovery. Can't do it.
You say you are not a noob, but I disagree. Every concern you have mentioned is on the first page of both the QA section and general section. Read before you brick.
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Lost in a paper bag again...