{Began} (arxamenos). Not pleonastic here, but graphically
showing how Peter began at the beginning and gave the full story
of God's dealings with him in Joppa and Caesarea. {Expounded}
(exetitheto). Imperfect middle of ektith(886d)i, to set forth,
old verb, but in the N.T. only in Acts ( 7:21  11:4  18:26  28:23 ), a deliberate and detailed narrative "in order"
(kathex(8873)). Old word for in succession. In the N.T. only in  Lu
1:2  8:1  Ac 3:24  11:14  18:23 . Luke evidently considered this
defence of Peter important and he preserves the marks of
authenticity. It came originally from Peter himself (verses
 5,6,15,16 ). "The case of Cornelius was a test case of primary
importance" (Page), "the first great difficulty of the early
Church." Part of the story Luke gives three times ( 10:3-6,30-32  11:13f. ). See the discussion chapter 10 for details given here.