The tooltip says that "не так" can also mean "wrong." Could this sentence also mean that earlier, everything was wrong? If not, how would you say that things were wrong?
Yes, sometimes "не так" means wrong. "Все не так." means everything is wrong now and nothing else. If you say "раньше все было не так" there will be ambiguity and meaning will depend on context. To avoid this ambiguity you can add some words.
"Раньше все было не так как сейчас" - everything was different before.
"Раньше все было не так как надо" - everything was wrong before.
The simplest way to say "wrong" is using "плохо" or "неправильно".
"Раньше все было плохо".
"Раньше все было неправильно".
Right, but since none of those clarifications are here, it could mean either, couldn't it?
Literally, it means "Previously, everything was not so." so I would like to suggest that this option is also valid?
It's amazing how so many Russian phrases amd expressions share the same meaning. This literal translation makes a lot more sense in Spanish, as it translates, "Antes no todo era así, (Previously/Before then, not everything was like that)". "Everything was different before", of course, may sound more natural.
No. This sentence means that earlier, everything was better or differently.
What is the difference between everything and everyone ? I always saw всё in both cases
"Everyone" is все (vsye). "Everything" is всё (vsyo). It can be confusing because people very often write 'е' where they mean 'ё'. Russians can easily get the difference from context, typically, but for learners it's tough.
Is "before" necessary, since it's kind of implied in the Russian sentence?