"You turn that way."
Yes, but here there is no difference, other than formality. そちら is the standard, "proper" form, while そっち is the casual, shortened form. Given that this is the case, I don't know why using そちら instead of そっち is marked as incorrect. Also, "just go with it" sounds almost defeatist; questioning and working out the differences of linguistic nuances is how understanding is fostered.
I am confused with the particle usage of these two example. would this be correct: そっちを曲がります?
を is used sometimes to describe a "perlative case" with motion verbs, this expresses that something moved through, across, or along the reference of the noun that is marked.
In the case of「そっちに曲がります」you are describing a direction where 曲がります happens
And in the case of「『その角を』『左に曲がります』」you are basically saying "turn left through/along that corner", describing with を the trajectory of the path that you or another person is to take.
I think そっちを曲がります is grammatically correct but they don't say it like that because そっち and そちら are considered directional pronouns, so you use に there.
I know this is a basic sentence, but I feel like none of the English words had the proper Japanese translation associated with them, and it's only by memorization - not by using the context clues - that I will get this right. Usually I can at least see what ONE of the words is, and put the rest together from there.