Questions

[Expected]

I find myself lacking answers and general knowledge when it comes to game mechanics and rulings. If you don't mind, I have some questions I'd like to get answers to?

1. I am confused about movement and adjacency in combat. On a square grid, does it take 5ft of movement to move diagonally, or 10? And are you within 5ft of an enemy if you are diagonally across from them? Are you able to attack diagonally?

2. If an ally is occupying a space you need to move through, does it cost extra movement or is it assumed they'll let you pass? What about enemies? Would the second example require an ability check? Do defeated creatures occupying spaces become difficult terrain?

3. What are the interactions between swimming and wearing heavy armor? Is it assumed that you behave normally in water (1/2 walking speed unless you have a swim speed, attack at disadvantage, hold breath up to 1 min + Con modifier) like unarmored or light/medium armored allies or are there extra penalties?

4. Can spells with the V requirement be cast quietly while stealthing? Am I correct that you'd need to stow your weapon to cast a spell that has the M component if you have a shield and sword but you also have the War Caster feat? How do reactions work if I don't have War Caster and both hands full but want to cast Shield/Absorb Elements? Would I need to drop or stow my sword on my turn?

[Lunali]

1. Diagonals count as being within 5ft. Most groups use 5-10-5 for diagonal, though some will do otherwise. This means the first diagonal is 5ft, the second is 10 and it switches back and forth. This results in distances that are close to what they would be in reality.

2. Other creatures spaces are counted as difficult terrain, costing double to move through. Allies are assumed to let you pass, hostiles must be larger or smaller by at least two size categories to move through their space. There are optional rules to pass through enemy spaces with ability checks. Defeated creatures may or may not be difficult terrain at DM discretion.

3. There are no changes in the rules based on armor, though many DMs rule otherwise.

4. Spells with verbal components must be spoken clearly and with specific resonance, meaning they aren't likely to be quiet. Usually people with war caster will find a way to have their shield or weapon be the material component of the spell that they're casting, but if they are unable to do so, one will have to be stowed (usually weapon since shield is an action). You would have to drop/sheathe your weapon on your turn to cast shield or absorb elements as a reaction.