Spanish language Q&A Forum

Hi, being back after a few months, I noticed that all example sentences use indicative mood, while the one in the lessons was in subjunctive:

De habérmelo explicado antes, no me hubiera enfadado tanto.

Why isn't this conditional, ... no me habría enfadado tanto?

A little off topic, but consider:

1. donde, adonde/a donde

2. dónde, adónde/a dónde

and for that matter (or maybe especially for the case of), 

3. quizá, quizás 

Within each group the various options can be used interchangeably. But what factors influence the chosen form? For example do some people tend to use the same form all the time? Do people just randomly use all the forms equally? Do some localities tend to use one form more than others? Is there a pronunciation efficiency issue (similar to y and i  or  o and u, but not a hard-and-fast rule)?

I guess my questions especially apply to quizá versus quizás. 

When would be appropriate to use formal and informal second person?

For context, I'm planning to speak mostly with my Mexican family members, many that I'll be meeting for the first time or for the first time in many years. Most of them are older than me (I have one younger brother who speaks mostly Spanish). Would it be better to speak formally to the older family members, or informally because they're family?

Would you start formally with strangers (esp. those who are older) and then at some point be able to drop formality as you become closer to people, or as they express to you that it's okay (similar to Korean and Japanese)?

I wrote "y que este año sea" instead of "y que sea un año". I asked a native speaker who said my answer was fine and that "this place just wants you to speak a certain way, you can't trust it."

Yo vuelvo y yo regreso  es la misma acción en español 

please help me understand why we use tengo/tiene and not estoy-soy.