mathsprofrockstar
Regarding the parsing of 42
Piped is an extra word (it goes with 2Dn's eventual entry. COTE has first 2 letters replaced with a 4 letter brass instrument)
Definition is "developmental stage" (e.g. butterfly)
"of" in the wordplay means you require a reversed adjectival form meaning "like an old script" (six letters) and ending in -IC, without the C. The old script is defined in Chambers thus
"an ancient alphabet used in Celtic and Pictish inscriptions, its letters consisting of sets of parallel lines meeting or crossing a base line (the corner of the stone monument often serving as the base line); any of its twenty characters; an inscription in this alphabet."