Question about horses

[alnaperera]

I am writing a sort of fantasy adventure thing and it involves horses. I have no experience with them whatsoever, so I have a few questions.
1) would a horse be okay with a trip that's ~15km, roughly 100m drop but with minor ups and downs and a pretty low grade throughout (say a maximum of ten degrees for very short stretches, sustained is more like one degree)? How long will this take? What about the return trip?
2) how would they react to this being at 2 in the morning? One horse is the rider's best friend pretty much, the other horse has never met the rider before but assume it's a nice horse. The second rider is also very experienced, just not with this horse.
3) how will the react to a bicycle being a part of the party?

Editing to add a bit more context.
The party consists of the following:
1. Horse A and character A, both used to each other (in town, around town, exploring hills, committing crime together).
2. Horse B and character B. Horse B is my biggest variable because they will appear for just this trip, that's it. Generally used for riding around farms and getting to nearby cities and stuff, I don't imagine this horse being one of those big farm horses. Character B is from a culture that is very horse based and has been riding since she feasibly could, mostly training with war horses.
3. Character C and bicycle. Character C has no riding experience whatsoever and needs to arrive at the destination in reasonable shape, hence the bicycle.
The trip happens early in the morning what would be the rough equivalent of northern hemisphere early March, temperatures would be in low single digits C and warming up slowly to low double digits.
The roads are reasonably well lit for established cultural reasons.
Character A and Character B can both see in the dark much better than the average person.
They also need to start the return trip almost immediately afterwards, though they can reasonably get some rest about 2 kilometers in.

Comments

[azurelunatic]

So Horse B is going to be a comfortable riding horse who may or may not have draft training. Since Character B is used to war horses, this is the equivalent of going from a manual transmission racecar or maybe a Saab to an automatic transmission minivan. The horse will be slower, calmer, less likely to react angrily to a snapping stick, less likely to kick a stranger, not as maneuverable unless one of the farm teenagers with ambitions has been teaching it dressage-type moves for fun, potentially not as responsive to subtle commands. (Some horses are trained to respond to knee commands to turn as well as rein commands, more likely in a war horse where the rider will need their hands for weapons.)

If this is Character A's family's farm, Character A will likely assist Character B in introducing themselves to Horse B, and will probably make sure that Character B has a good stock of Horse B's favorite treats, and will tell Character B how Horse B likes to be touched. So Character B and Horse B should get off to a good start together. And Character A will have likely picked the most suitable horse for the situation -- one who is good with night rides on these roads, one who accepts strange riders, one without any unacceptable tricks, and one who won't have to be worked the next day.

Character B will be on the lookout for all kinds of annoying tricks that a tempermental war horse might do, but this horse is most likely to offer only the old saddle band trick (which Character B will automatically be on the lookout for, and might not even notice that they're looking out for it, because it's such a very very common horse trick).