Another attempt.
"5.8. It is forbidden to use spell scrolls of levels 4 and 5 without building the corresponding level of the Mage Guild (MG) in any of your castles.
If the starting castle does not have the corresponding level of MG, then you must proceed according to subparagraphs a, c of paragraph 5.2."
Hence, 3 conclusions:
1. It is allowed to use spell scrolls of levels 4 and 5 after building the corresponding level of the Mage Guild (MG) in any of your castles.
2. If the starting castle does not have the corresponding level of MG, then you must proceed according to subparagraphs a, c of paragraph 5.2. /i.e., starting as the Swamp faction, you can use, for example, a Town Portal scroll after opening Pandora's Box with all the magic of the land, regardless of whether the hero opening it has the required wisdom/
3. If the starting castle has the corresponding level of MG, then paragraph 5.2 "c" does not apply to scrolls /i.e., starting as the Castle faction, you cannot use, for example, a Town Portal scroll after opening Pandora's Box with all the magic of the land, regardless of whether the hero opening it has the required wisdom/
You wrote everything correctly, but I cannot agree with point 3 of your post. According to the Rules, you must fulfill one of the conditions to use a Town Portal scroll (building the Guild, Pandora's Box, the Book...). There is no reason to believe that it is impossible to use a Town Portal scroll when several conditions are met simultaneously (building the Guild, Pandora's Box, taking Earth Knowledge).
