Learn English – meaning “move against each other”

Each and every uses the repetition for emphasis. As Wiktionary says:

Each without exception; used for emphasis.
　　"Do not leave without checking each and every door to make sure it is locked."

Until and unless uses the repetition for emphasis as well. This phrase, however, is somewhat less common, and I think it's used mainly in formal contexts. (I was unable to find a dictionary that listed until and unless.)

To give you an idea of relative frequency, here are the terms I searched for in COCA, along with how many results I found for each search term:

  each and every       1500
  every and each       2

  until and unless     58
  unless and until     137

You'll notice that each and every is a fixed phrase which doesn't occur in reverse order, but until and unless is actually more common the other way around. (Thanks to J.R. for pointing this out in a comment!)

Well, IMO, both are correct.

In English, certain words require some preposition, and 'walk' is the word here. Other options of preposition after the verb include along, down, and even up! I think they might have a hairline difference. Maybe, the next word shows some direction?

If a road is going downhill, it could be 'walk down the road'; if it's running toward some hill or slope, we may say 'walk up the road', and in a case, it's flat or plain, 'walk along the road,' maybe! I also feel that along has 'long' in it and thus, it might have to do something at the 'stretch' i.e. walking with the length of the river?

Interestingly, it's also used as an idiom, and there too, they are the same!

along/down the road: in the future, especially at a later stage in a process