I do not know if you bought the ticket from the same website or company as I did or not. For me it states clearly that you can pick up your ticket any day convenient to you BUT YOU HAVE TO PICK THE TICKET AT JR KYOTO STATION NOT AT SAGA TRAIN STATION NOR ANY JR STATION. I recommend you to check if what I said is true for your case so you have enough time to get to JR Kyoto station to pick up your ticket. And at JR Kyoto station there is specific wicket to pick up ticket made from online reservation. It is the most left line. Just ask staff there. You do not have to wait in line.

嵐山から亀岡へ乗るとして、座席ボックス番号は偶数、座席はA(窓側)とB(通路)が進行方向に向かってのお席になります。

I think that change fee will be taken. Please consult at the Ticket counter of JR-west.

We walked down through the Bamboo forest which was fascinating and simply boarded the train again at the lower station.

Their website says you are able to buy tickets in advance, but not online: Tickets can be bought from Midori-no-Madoguchi counters at major JR West stations, or at major domestic travel agencies, beginning at 10 a.m. on the day 1 month prior to your ride date. You can also purchase tickets at the following locations: Central Japan Travel Center, Chubu Centrair International Airport Kansai Tourist Information Center, Daimaru Shinsaibashi Kansai Tourist Information Center, Kyoto But if you're going to buy them on the day, they can sell out pretty quickly and you'll be left with standing only tickets. My advice for on the day sales would be to get there early, buy your ticket, then go check out the bamboo forest which is just around the corner.

On the right seat in fall (changing leaves season)is one of the best time for this romantic train with light up at night along the way. It's really enjoyable but need advaced booking. But spring time is also ok gor blooming flowers along the way.

Yes, book the 10:29 am return! Do not book the 11:29 am train. I went one-way, but this is what I saw and heard as I was getting off the train: people who were returning to Saga-Arashiyama stayed on the same train and apparently already had tickets to do so. I think it loads quickly (as all trains appear to do in Japan) and just goes back the same way it came. I'm pretty sure there's only one track. Kameoka is a very small station. No worries even if you do have to get off the train for some reason. Definitely buy both legs of your trip in advance. It's popular and crowded, particularly this time of year (i.e., fall foliage viewing).

The trains did not stop at the station, but I think you can request it to stop. I am unsure about tickets.