Is it okay if I do my Spanish for English speakers and my English for Spanish speakers at the same time? I know most people do the reverse tree after the normal tree, but will I retain the information if I do both trees at the same time?
I don't know about the reverse tree and the normal tree at the same time but I'm doing Italian for English speakers and Italian for Spanish speakers (my native language) at the same time, and the same goes for French. It definitely works for me, doing 4 trees is helping me to retain information much easier and to understand some stuff otherwise I would struggle to understand.
Although most people wait to do to the reverse tree until they've finished the forward tree, others do them both at the same time and enjoy it. So it's up to you. If you try it and it's too confusing, then you can concentrate on the forward one for a while first, then pick the other up later. I would say go ahead and give it a try. You might like it better that way!
I started the Spanish-to-English after finishing my Spanish tree and I'm glad I waited. It...definitely gives your knowledge of indirect and direct objects a workout. It's also (unsurprisingly) a lot less forgiving of Spanish errors than the English-to-Spanish tree is.
There's nothing wrong with giving the tree a shot earlier than I did. Don't test out of anything, and do turn off the listening and speaking exercises.
What I do with the listening exercises on the reverse tree is leave them on, but after typing the English phrase, I translate it to Spanish out loud before clicking submit. Then I check it against the translation given at the bottom. This gives me good practice translating to Spanish, and sure enough, the question usually comes up asking me to translate from English to Spanish, so it helps there too.
That's a good idea! I've been getting the listening exercises despite turning off audio and listening, so this would be a good way to make lemonade.