Again (palin). Referring to Joh 1:28 (Bethany beyond Jordan). Palin does not mean that the other visit was a recent one.
At the first (to prōton). Adverbial accusative (extent of time). Same idiom in Joh 12:16; Joh 19:39. Here the identical language of Joh 1:28 is used with the mere addition of to prōton (hopou ēn Iōanēs baptizōn, “where John was baptizing”).
And there he abode (kai emenen ekei). Imperfect (continued) active of menō, though some MSS. have the constative aorist active emeinen. Probably from here Jesus carried on the first part of the later Perean Ministry (Luke 13:22-16:10) before the visit to Bethany at the raising of Lazarus (John 11:1-44).