yes it's the same for the rounded 2 pins.

1) If u wanna explore every temple and place of interest.  It is not enough. If travel for relax and beachs sightseeing. Yes.. it ia enough.. cos only 2 main beach and u can explore 1 temple n taejedong
2) u either rent wifi or rent phone or sim.. pls refer to page 30
3) yes.. i use Tmoney..but it is not really good la.. cos if u buy day pass only 4000 won. I stupid and miss this day pass n travel with TMoney.. it cos cost 1500 won each station. The day pass is for mrt. Bus i not sure cos i use tmoney
4) major attractions. . Gwangali beach (rainbow bridge nice for night time sitting there drink coffee and see ppl pass by with beautiful bridge). I spent 2 nights at there
jalgachi market.. wet market for seafood.
Piff zone - like jalan petaling or night market.. selling thing
gamcheon village - santorini korea.. destination for photographer
beomosa temple - temple with lantern
haeudae beach - beach
shinsagae department store - shooping complex
another temple but i forgot the name...
taejedong - sightseeing

and some shopping complexs
5) a lots guesthouse. . Can find in agoda.com depend on ur criteria u needed
6) i done ittenary but i didnt follow cos not enough time.
7) i heard it expensive. But i not sure.. walking in busan quite comfortable because even it sunny but it windy and cold like genting weather
8) yes but i went to place of interest with public transport, map and mrt.
I just back from busan yesterday.  Now in seoul.

I spend 3 days in busan. I landing on incheon then strait to busan by ktx. Ktx u must book on internet(refer back to page 28 or 29 if i not mistaken, other forummer share the link)

Once i arrive seoul station i take my 3 days pass with the printed ticket that i booked at information counter.They will check ur passport and giv u 1 card.then u need go to ticket counter and get ur ktx ticket.  Ktx to busan quite convenient. It like every 15 to 30 minutes got train to busan - seoul. It take 3 hours ride, go toilet before u get into train. Inside no toilet if i not mistaken. Free wifi inside the ltx too but u need to install their apps. Just install lo.. no harm.. inside train better check ur car and seat no. Dont ever changed seat if u c other unoccupied seat cos other terminal will hv other passengers come in n looking their no accordingly.