I'm by no means an expert, but I will try my best to answer as much as I can!
How do you perform a push block? (Knocking the opponent away after blocking)
This one I know for sure: While blocking, press

. That'll push away any aggression!
Sometimes when a character blocks, they flash white for a frame or two. What does that mean?
There are a variety of states in which a blocking character will flash, that I'm aware of, so I'm not sure which one is on your mind. If you block at the last moment, you can essentially do something called a "Just Defend" maneuver - Which blocks the attack and gives you some meter, I believe. It may also reduce chip damage? This is great when the opponent is spamming projectiles, because with proper timing, you can turn that into your advantage.
The Cross Canter also makes your character flash on block, though it is usually green and always is followed by a counter-attack.
I fear I might be overlooking the specific instance you're thinking of, but hopefully this information was slightly useful despite that!
Are there any specific rules on when a throw attempt will connect or whiff based on the opponent's actions (assuming you're in range)?
If you go into training mode, you can turn on hitboxes on the characters. Try performing a throw with that enabled - it will show you exactly where the opponent's hitbox needs to be in order to have the throw connect! Otherwise, be aware that opponents can interrupt a throw in many ways: Attacks that come out faster than your throw, jumping away from your throw, and also something called
teching your throw. If the opponent presses



while you are attempting a throw, and their timing is right, they'll break that throw.
Would someone be so kind as to explain these and any other basic mechanics pleeeease?
I highly recommend the following video from the Fighting Foenatics:
It's a bit of an older video, but the basics in there are still really solid, and provides a good foundation to the mechanics. The start of the video is probably all stuff that you're already familiar with from other fighting games, but it gets into TFH specific mechanics deeper in. There's some jargon in there, though - so if any of the terms are unfamiliar, please don't hesitate to ask!