the ''1/4'''' and ''cola ends'' are not proper terms, nor are they ways to judge anything about the plant, other than appearance. you certainly weren't a science teacher...
pistils don't matter unless you are pollinating. and referring to a cola in the manner you're speaking would mean to check the apical flower cluster on the central stem/stalk. a topped plant will have many apical flower sites, one not topped will have one main apical growth with laterals lagging behind.
the start time of flowering is the first day after 12 hours of uninterrupted darkness AFTER the plant has reached sexual maturity. if no preflowers before 12/12, no flower yet, and your time is moot.
first day after first dark cycle after first full sexually mature flower on at least one alternating internode.
science is cool. i used to be a teacher too.