Quote from JooBear >>

Action surge, quickened and war caster are the exceptions and not the rule - Gods can cast two levelled spells per turn, mortals cannot

It's easily done even without Action Surge, War Caster, or any metamagic. First cast a leveled spell, then try to walk away from an enemy and provoke an opportunity attack, then cast a leveled reaction spell in response to that attack like Shield or Hellish Rebuke. Heck, cast a leveled spell and then jump off a cliff and cast Feather Fall, which is also leveled. Your premise is incorrect.

Quote from JooBear >>

Action surge, quickened and war caster are the exceptions and not the rule - Gods can cast two levelled spells per turn, mortals cannot

Quickened Metamagic is not an exception - in fact - it specifically triggers the bonus action spellcasting rule because of how it works. So it actively stops you from being able to cast multiple levelled spells.

And the others aren't exceptions to the bonus action spellcasting rule because they don't even trigger it to begin with.

As for the gods and mortals bit - I have no idea what you're talking about. Is that actually a rule anywhere in the books?

Quote from JooBear >>

Action surge, quickened and war caster are the exceptions and not the rule - Gods can cast two levelled spells per turn, mortals cannot

 Admitting that you're wrong is not a bad thing. It's ok not to be right.

I will add two qualifiers to my image, but I would like to know if people can think of some situations that it does not apply to because I can't think of any.

1. The image assumes we are talking about what you can do "on your turn"
2. I used the phrase: "You can cast a cantrip with a casting time of an action",  which is the PHB wording. Xanathar's guide expanded on it to say "you can cast cantrips with a casting time of an action"

Exceptions still aren't the rule lol cherry-picking extremely specific examples to try and side step the rule just shows that i'm right lol 
Yes there are times when you can cast two levelled spells if the stars and moons align and you get your war caster or action surge or reaction or whatever it is in limited circumstances but openly you cannot cast two levelled spells in one round of initiative 

I've no idea what book its from but I found it here 
https://www.youtube.com/watch?v=ZcR2iBeF2zo

Gods can use two levelled spells in a round of initiative, Legendary monsters cannot - hence why Liches can only use cantrips as Legendary Actions
It's supposed to be difficult to manipulate the weave and cast magic in DND and a round of initiative is only 6 seconds, how much magic do you think a mortal is capable of commanding in 6 seconds? 

Youtube videos aren't RAW.

Quote from JooBear >>

Exceptions still aren't the rule lol cherry-picking extremely specific examples to try and side step the rule just shows that i'm right lol 
Yes there are times when you can cast two levelled spells if the stars and moons align and you get your war caster or action surge or reaction or whatever it is in limited circumstances but openly you cannot cast two levelled spells in one round of initiative 

Incorrect. There is no such rule. There is a soft limit, which is action economy, but anything that lets you get around that will allow more than one leveled spell a turn. This is explicitly mentioned by the writers.

From the Sage Advice Compendium:

Is there a limit on the number of spells you can cast on your turn?

There’s no rule that says you can cast only X number of spells on your turn, but there are some practical limits. The main limiting factor is your action. Most spells require an action to cast, and unless you use a feature like the fighter’s Action Surge, you have only one action on your turn.

If you cast a spell, such as healing word, with a bonus action, you can cast another spell with your action, but that other spell must be a cantrip. Keep in mind that this particular limit is specific to spells that use a bonus action. For instance, if you cast a second spell using Action Surge, you aren’t limited to casting a cantrip with it.

Does the rule on casting a bonus action spell apply when you take a bonus action granted by a spell?

The rule on casting a spell as a bonus action applies only on the turn you cast the spell. For example, spiritual weapon can be cast as a bonus action, and it lasts for 1 minute. On the turn you cast it, you can’t cast another spell before or after it, unless that spell is a cantrip with a casting time of 1 action. Until spiritual weapon ends, it gives you the option of controlling its spectral weapon as a bonus action. That bonus action does not involve casting a spell, despite the fact that it’s granted by a spell, so you can control the weapon and cast whatever spell you like on the same turn.

Can you cast a reaction spell on your turn?

You sure can! Here’s a common way for it to happen: Cornelius the wizard is casting fireball on his turn, and his foe casts counterspell on him. Cornelius also has counterspell prepared, so he uses his reaction to cast it and break his foe’s counterspell before it can stop fireball.

Quote from JooBear >>

Exceptions still aren't the rule lol cherry-picking extremely specific examples to try and side step the rule just shows that i'm right lol 
Yes there are times when you can cast two levelled spells if the stars and moons align and you get your war caster or action surge or reaction or whatever it is in limited circumstances but openly you cannot cast two levelled spells in one round of initiative 

The point is that you can ALWAYS cast two (or more) levelled spells on your turn, provided you have the action economy to do so and none of them use your bonus action to cast.