I've now beaten v4; here's more ROT13 comments
V yvxr guvf irefvba orggre; fxvccvat n fvatyr bar bs gur Cher Xrl pbhagf (cerfhznoyl 6 be 8, gubhtu 9 be 12 nyfb jbexf) fb lbh pna trg gb 13 naq trg evq bs Benatr (guhf yrnivat 7 sbe Oynpx) vf n orggre fbyhgvba (va zl bcvavba) gura hfvat gur Oebja nhen gb whfg fxvc ahzoref ragveryl. Ubjrire, gurer pbhyq fgvyy or na vffhr urer: gung -1 Znfgre -> Cher qbbe pbhyq or hfrq va gur zvqqyr bs qenvavat n pbybe, nyybjvat lbh gb (sbe rknzcyr) hfr n pbzovangvba bs 2f naq 3f (be 3f naq 4f, be 4f naq 5f, naq fb ba) ba n fvatyr pbybe, juvpu fbeg bs tbrf ntnvafg gur cbvag bs gur chmmyr. Vg jbhyq or arng gb rafher gung gung -1 Znfgre -> Cher qbbe pna bayl or hfrq evtug nsgre (be evtug orsber) qrfgeblvat n pbcl bs gur ovt Cher Xrl vapernfvat qbbe, ohg V'z abg fher ubj lbh'q qb gung. Gung orvat fnvq, gnxvat nqinagntr bs guvf bcgvba pbhyq znxr n uneqre irefvba bs gur chmmyr: vs gur Tyvgpu Oynfg Qbbe jnf ercynprq jvgu n frpbaq -1 Znfgre -> Cher qbbe, lbh'q or sbeprq gb hfr guvf bcgvba sbe Plna Xrlf, naq cebonoyl sbe fbzr bgure Xrl pbybe nf jryy. V jbaqre vs gung irefvba bs gur chmmyr jbhyq or cbffvoyr?
Nyfb, bhg bs phevbfvgl, jung jnf gur vagraqrq fbyhgvba gb i1? V qba'g frr n jnl gb trg gb tnva na rkgen Cher Xrl, naq guhf trg gb 13 Cher Xrlf, fb rnfvyl va gur bevtvany irefvba bs gur chmmyr...
RQVG: Nyfb, jul qvq lbh nqq n guveq artngvir Znfgre Xrl orgjrra gur irefvbaf? V qba'g frr jul gur Znfgre Xrl nzbhag unq gb or vapernfrq.