Salthorae
Imperial Mountain Dew Taster
For instance, just about everybody knows or has seen magic missile, fireball, cure wounds, etc. Stuff that’s recognizable on sight
I think this speaks to baseline assumptions about each game world you're playing in at the time or you're confusing "everybody" in game with all the players. Sure we've all seen magic missile and fireball, etc. But have your 1st level barbarians with the outlander background? Your 1st level urchin rogue? Maybe if they adventure with an arcane caster they've seen some of that stuff or some "divine miracles" of cure wounds. At least at my table, there is no baselin assumption that anyone is familiar with spells or magical effects. Even wizards if they don't have a spell in their books have to make a check to know about spells and effects they're seeing. Otherwise (to us) it removes mystery from the game, and it gets boring.
If they do, great, play on. If they don't, then welcome to the club - I have some cool stuff to show you!
This is the type of language that [MENTION=6812658]Seramus[/MENTION] was talking about. If people agree with you it's "in the club" and "cool", implications there are that the other side is wrong and uncool.
Can a toad die without knowledge of how polymorph spells work?
If so, then we don't need to establish what the character knows about this spell.
Sure, but it's still going to have to take action from another player to do so. Even if the toad runs into the path of another player, most people IRL aren't going to step on a frog in their path, they're going to go around or over it, so why would you step on your friend who was just changed into a frog?
It seems like you keep wanting to ignore the turn based action economy mechanics of the game for this hypothetical frog-fighter to suicide. At which point you're not playing 5e anymore and that is fine. But in 5e, it still takes deliberate action of other players to achieve this frog suicide. Otherwise the DM is just then forcing one of the other character's actions to achieve this frog's suicide by saying that the frog-fighter is squished under the charging barbarian's boots, or is impaled on a blade of someone as they jump up.
I think it is time to accept toad suicide is a perfectly legitimate strategy for some D&D players, but not all.
Other than that, twenty pages in it's time to recognize when you're being trolled, I'd say.
Luckily on my browser we're only at 11 pages.