Translation:When I was a girl, I used to walk by your house.
wilmie; "I would walk" is one option of translating "caminaba", but Duolingo does not accept it. "Caminaba" is in the imperfect tense.////////One use of the imperfect is to describe things that a person normally would do in the past (note: 'would'). For example, "When I was young, I would play football every Saturday" = "Cuando yo era joven, jugaba el futból todos los sábados"..............or......."When I lived in Florida, I would swim every weekend" = "Cuando yo vivía en la Florida, nadaba todos los fins de semana". I have reported this to Duolingo and hopefully they will change to allow the "would" option for imperfect tense.//////////So, back to the present sentence: a correct translation could be: "When I was a girl, I would walk by your house."
Caminaría is the conditional. However, "would" is used in different ways in English. Here it's not a conditional.
"We can use ‘would’ to talk about repeated past actions. Often either ‘would’ or ‘used to’ is possible."
However, Duolingo doesn't usually accept this use of "would" for some reason. Maybe they are worried that people will get it confused with the conditional?
My understanding is that "por" is fairly vague and can mean a lot of things including "by" or "through" among other things.