I learned just from a lot of watching people on youtube and in-game and just practicing in multiplayer. This game is really hard to learn compared to a lot of other games.

Toribash is not all about openers. In order to be a good toribasher, you have to learn to use all different types of openers. Try playing abd with the simple noobclap against a snapkick and see if you can block it. Than you ask yourself the question, what do you do after you block. Once you have mastered the noob clap, you will often find playing matches easier and understand toribash better because (almost) all moves originate from the noobclap so once you understand the noobclap, you will be more successful at playing toribash and finding a good opener

What is the reaction timer?

it is customizable but usually 20 sec (I think)

the reaction timer is how long you have each turn to move your joints before turn ends

I never really used tutorials or tested my moves in Singleplayer. I just practiced a lot and eventually got good. xD