Do my players know the specifics of an enemy’s attack

I’ve looked through the PHB and the RPG Stackexchange but I haven’t found anything regarding the following:

Many monsters have some kind of special attack or action that inflict a certain status on the PC. Usually the PCs can remove or escape this status by doing a certain kind of action.

E.g. The Fire Elemental can light PCs on fire and you need to expend an action in order to put it out.

How do I handle this information in regard to my players? Let’s take the Fire Elemental’s special feature as an example

  • Do I tell them that they are on fire and can put it out as an action in their turn?
  • Do I just tell them that they are on fire and let the players figure out what to do (which is obvious in this case but maybe not in other cases)?
  • If the latter is the case do the players lose their action if they attempt a wrong solution?

I usually tell my players what they can do to get rid of the status but I’d be interested if there is a rule somewhere that states how to handle this situation

How do I adjudicate a player trying to sweep kick an enemy’s legs to knock them down?

I’m new to D&D. I already read both the Player’s Handbook and Dungeon Master’s Guide (I’m mastering) and I would like to know how I could handle this situation:

A player wants to do a sweep kick on an enemy’s legs and knock him down. He rolls a 20 and does the damage, but what about taking the enemy down? There is no rule that covers it.

Following the rules, the player would have to do a specific action to try to push the enemy down, and there would have to be a resisted check to see if the player can actually drop the enemy, so how could I deal with that?

What is the lowest-level spell combo to give disadvantage to an enemy’s specific save, without running into follow-up concentration issues?

What I’m trying to do is debuff an enemy’s stat so that I can hit them with a “save or suck” spell like dominate monster, and be more likely to succeed.

The problem is, I’m running into concentration issues because most spells that debuff a single stat like Bestow Curse use concentration, and thus I cant use them in conjunction: The moment I cast Dominate Monster, Bestow Curse is removed.

Hex also will not work because it only impacts ability checks, and not saves.

To clarify, I am a Warlock who wants to cast powerful disabling spells only when they have a high chance of success (so typically Wisdom has to be the weakened modifier). However, I am open to answers outside of that class, as well as any spell combos that specifically function as

  1. Weakening the the ability save for the second spell without utilizing concentration, and

  2. The second spell being a powerful, one-save spell of concentration.

What spells would be the best for this kind of combo, given that only I can cast the spells?

What happens if a Divination wizard uses the Portent feature to replace an enemy’s initiative roll, when the DM rolls once for a group of enemies?

Say 4 goblins ambush a level 2 party, everyone is surprised but the Wizard decides to use his Portent feature to influence the initiative roll of the enemy. One of his portents is a natural 1, and he uses that die to replace the initiative roll.

Do all 4 of the goblins’ initiative change to 1 or does just one goblin change?

Here’s what I got from a reading of the PHB:

PHB 189

Initiative

… When combat starts, every participant makes a Dexterity Check to determine their place in the initiative order. The DM makes one roll for an entire group of identical creatures, so each member of the group acts at the same time…

Emphasis mine. Reading the bolded text, it seems that in cases of identical creatures, Portent can effectively cripple the entire initiative of the opposing team.

However, when you read the first sentence, it seems that the entire group shouldn’t be crippled by a single portent roll as each creature should be rolling separately and the bolded text really just says, “hey, don’t waste your time on rolling for each goblin. Just roll once and they all go together.”

A big factor of my hesitance to rule on the side of the first interpretation, is that it seems too overpowered for a 2nd-level feature.

So which is which? Am I missing something?

Is there a spell that would give my character insight to an enemy’s weaknesses and resistance?

When I first heard of True Strike, I originally thought it was quite a powerful cantrip that would allow the castor to sacrifice 1 attack in order to be granted insight into the target’s elemental weaknesses and resistances. It reminded me of my first campaign when I walked into it at level 4 and felt lost hearing my DM state “your attack seems to have done nothing” even when I knew it was a hit.

However, realizing that was a false understanding of the rules, I was wondering if there was a spell that would give you such insight?

For the Charger feat, is it possible to move at least 10 feet in a straight line while staying within an enemy’s reach?

The Charger feat lets you make a bonus-action attack with +5 to the damage roll if you take the Dash action and “If you move at least 10 feet in a straight line immediately before taking this bonus action”.

When playing on a grid, am I correct that you would very often be able to move around the enemy to get this benefit, often without provoking an opportunity attack?
(On a 5-foot grid, excluding obstacles, there are a minimum of 8 squares within an enemy’s reach; from one diagonally adjacent square to the next are 3 squares.)

Can I change my movement/action in the middle of the turn after an enemy’s reaction?

Imagine I’m a rogue and I see an opponent 50′ away. In my turn I want to use my movement and my Dash bonus action (Cunning Action) to approach it and use my Action to attack.
Then, after moving just 10′ (or more, I guess it may change the answer), another opponent had readied it’s action so as a reaction it attacks me, and hits me so hard I don’t want to go hit that opponent anymore.

  • Can I just stop my current movement and move elsewhere/back?
  • Do I have to finish my movement and then use the Dash to move away? If that’s the case, I assume it depends on how much I’ve moved to know what can I do.
  • Does changing this imply some sort of penalty?

Thanks

Can you cast Hunger on an enemy’s item and have it move with them?

Hunger of hadar reads:

A 20-foot-radius sphere of blackness and bitter cold appears, centered on a point with range and lasting for the duration.

When casting it, would the wording of the spell allow my warlock to cast the spell on the enemy’s weapon or a necklace that is worn, (a point I can see), and allow the spell to move with target?

Can you cast Hunger on an enemy’s item and have it move with them?

Hunger of hadar reads:

A 20-foot-radius sphere of blackness and bitter cold appears, centered on a point with range and lasting for the duration.

When casting it, would the wording of the spell allow my warlock to cast the spell on the enemy’s weapon or a necklace that is worn, (a point I can see), and allow the spell to move with target?