I would recommend to get Hemp og Jute from a bondage supplier, like Twistedmonk. That is where I got my hemp rope, all precut to length and each ends are bound with thin rope to preven unraveling. If you need it cheaper then go to a sailing/boat shop and get braided cotton rope, se picture below. The braided does not untwine are laid rope does. Also the cotton on the outside is not too slippery and the rope is felxible as well. Test it by laying it in a U shape and give a small press, the "eye" should be small, of the rope is to rigid it will make a large "eye".
Climbing rope I do not recommend, it is to rigid and it flees to much, also it is to slipery on the outside. This is because a climbing rope should work that way! If the climber falls the rope need to flex to dampen the fall, it should have a certain friction to both slip and hold at the preice moment the climber wants etc. And thus normal knot like the Square knot will be to loose because of the slippere outer skinn and the stifness.
So a a rope with kevlar(or other fiber) core and then braided with a middle section and then a braided cotton outside is my second recommendation.
The best way to tie is also to use a "double rope", find the middle of the rope and fold the two ends. Work from the middle by using both ends. By doing this you will have shorter rope to work with, you will less likely cause a rope burn, you get more rope layers to get a good nice cuffs and it is easy to tie of the ends with a square knot.
So:
1. Get either a rope kit for twistedmonk or if you by retail just get a long and cut it yourself. Use electicaltape two times with 0,5cm apart and cut in between the tape, then use a lighter or candle to melt the ends. Works only on rope with synthetics, so hemp/jute you cant melt the ends as it is all natural. But cotton with fiber core, the core melts and fasten the cotton as well.
So lengt just get as long as you need and cut it to desired lengths when you get home.
2. Yes!
3. Get several lengths, also for hips/waits and chest. Perhaps a Karada (full body harness) length.
4. Diameter. I would recommend 4-10mm, depending on your style and what you are gonna tie and how many wraps in the coil you are using. Personally I use 6 or 8mm Hemp from twisted monk, and 6 and 8mm on the cotton style wich I had before going for hemp. The Hemp is laid rope though, but it works just fine.
If youre having more questions just ask in forum or PM!
Best regards
The Bondageking..... A title a band gave me after helping them with bondage and Shibari suspension for a music video!
Yeah, I'm a real bondage/shibari/Kinbaku junkie. LOL
- they do a good line in welded chain as well 
