having had perfect understanding = having followed up accurately.
all. The 1611 edition of the Authorized Version omitted this "all".
from the very first = from above. Greek. anothen. As in Mat_27:51 (the top, Mar_15:38). Joh_3:3, Joh_3:7 (again), Joh_3:31 (from above); Luk_19:11, Luk_19:23. Jam_1:17; Jam_3:1, Jam_3:17. It may mean from the beginning, as in Act_26:5, but there is no need to introduce that meaning here, as it is already in Luk_1:2. Moreover, havingunderstood them "from above", he necessarily understood them from the very beginning, as well as perfectly, or accurately. The greater includes the less.
in order = with method. most excellent. A title of social degree, not of moral quality. See Act_23:26; Act_26:25.