Can “partial” surprise happen? Would it be an acceptable rule?

I’m thinking the "surprise round" rule just isn’t fair. Say there’s a 2 vs 2 encounter (teams PC and Creatures (Cs)), then PC1 could notice the 2 Cs and PC2 just one of them. Also for the sake of discussion PC1 is mute for whatever reason, so he can’t quickly communicate with PC2 and he also plays last according to iniciative order. Then PC2 loosing an entire round seems unfair to me, because he could perfectly be taking actions against the C he found. Also if PC2 gets attacked by the Cs it would be doubly unfair, even if one has advantage and the other don’t, it’s 2 actions against none. So I figured you could ask PC2 to just turn around when it isn’t his turn during the surprise round, so as not to reveal the concealed C position to him and then, when he plays his turn remove the hidden C and let PC2 play as always…or if he gets attacked by hidden C before his turn he now sees it. What do you think?

If something happens “when an attack is made”, when does that something happen?

A select few features occur, not when an attack roll is made, but instead when an attack is made.

Three examples are the Protection Fighting Style, the Vengeance Paladin’s Soul of Vengeance feature, and the Arrow-Catching Shield magic item. These states (emphasis mine):

When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. […]

[…] In addition, whenever an attacker makes a ranged attack against a target within 5 feet of you, you can use your reaction to become the target of the attack instead. […]

[…] When a creature under the effect of your Vow of Enmity makes an attack, you can use your reaction to make a melee weapon attack against that creature if it is within range. […]

Notably, there are numerous other features that occur when somebody is targeted by an attack, or when somebody makes an attack roll, or when somebody is actually hit with an attack, but none of the features above specify any of those scenarios. Examples of features that do specify are the Mastermind Rogue’s Misdirection feature, the Lore Bard’s Cutting Words feature, and the Monk’s Deflect Missiles feature:

[…] When you are targeted by an attack […]

[…] When a creature that you can see within 60 feet of you makes an attack roll […]

[…] when you are hit by a ranged weapon attack. […]

As such, I’m unsure when the Protection Fighting Style, Soul of Vengeance, and Arrow-Catching Shield actually takes place. Are they before the target is determined? Before the attack roll is made? After the attack roll but before knowing if it hits or misses? After knowing if it hits or misses? After the damage is applied? Does it vary with each feature? Is it some other answer entirely?

Interaction between Telemechanics and a Glitter Boy Power Armor, what would happen?

A Mind Melter finds a functioning and unattended suit of Glitter Boy Power Armor. The Mind Melter decides to use Telemechanics on it in order to pilot it.

The Glitter Boy OCC states that non GB pilots can only operate the suit at a Basic level of proficiency while GB pilots default to the Elite proficiency. However, the Telemechanics power states that a Psionic can operate any machine at 80% scholastic skill expertise… but not which skill specifically, and all skills seem to be lumped under "scholastic" as per the general description in the Skills section.

The Mind Melter gets into a Hand to Hand fight while piloting the Glitter Boy and using the Telemechanics power.

Does the Mind Melter use the Basic as per the GB OCC description, the Elite skill somehow, the 80% "scholastic skill" as per the Telemechanics power (and if so, which skill does that translate as), or something else?

In short, what happens… and what level of proficiency does the Telemechanics power result in for the Mind Melter in Hand to Hand combat in the Glitter Boy?

Does Battle Cry happen before or after Initiative is rolled?

The Feat Battle Cry reads

When you roll initiative, you can yell a mighty battle cry and Demoralize an observed foe as a free action. If you’re legendary in Intimidation, you can use a reaction to Demoralize your foe when you critically succeed at an attack roll.

There are similar abilities, such as Hobgoblin Generals’ General’s Cry.

Do effects like this occur before or after initiative is rolled; specifically, does this (potentially) affect the target’s Initiative roll?

What happen if a Twilight Domain Cleric that shared his darkvision becomes unconscious or die?

The Eyes of Night feature from the Twilight Domain Cleric, introduced in Tasha’s Cauldron of Everything pg. 34, grants darkvision to the cleric:

You can see through the deepest gloom. You have darkvision out to a range of 300 feet.

It also allows the cleric to share this darkvision with willing creatures:

As an action, you can magically share the darkvision of this feature with willing creatures you can see within 10 feet of you, up to a number of creatures equal to your Wisdom modifier (minimum of one creature). The shared darkvision lasts for 1 hour. […]

But the description of the feature does not state what would happen if the cleric becomes unconcious or die, only state that it last for 1 hour. I can think of some interpretations for those cenarios:

  1. The cleric already used his action to share his darkvision, so he does not need to do anything and the sharing will last for the duration, regardless of what happen to the cleric.
  2. Since it is your (the cleric) darkvision, if the creatures goes unconscious that creature still have the darkvision and the feature, so it’s still shared. But if it died, a corpse does not have such a feature, so the sharing it’s cutted off.
  3. An unconcious creature cannot use it’s features, so, even though the cleric shared when he was conscious, once he becomes unconscious the sharing is canceled. Naturally, the same goes in the case if he dies.

Personally I think the second scenario it’s the more appropriate, but I’m not absolutely sure.

Is there any official rule that could help to determine what would happen in this cases?

If a creator of a Shield Guardian gives the control amulet to the Shield Guardian, what would happen?

There was an idea pitched at one of my play sessions earlier this week that has been gnawing at me. Suppose a wizard creates a shield guardian and gives the golem the telepathic command to take off the amulet and live a life of its own; what would happen?

Would the Shield Guardian become a sort of pseudo-warforged, following the original command? Would it just be stuck, standing there?

What would happen if a wizard calls a familiar in the Ethereal Plane and then returns to the Material Plane?

What would happen if a wizard summons a familiar (using find familiar) in the Border Ethereal, and then the wizard returns to the Material Plane (interrupting or ending the magical effects of etherealness)?

Would the familiar disappear due to the distance from the caster, since they are now on different planes?
Or
Does the Ethereal Plane overlap with the Material Plane (Border Ethereal) such that distances are preserved and the familiar remains in the Border Ethereal while the caster is in the Material Plane?

The Ethereal Plane
Its shores, called the Border Ethereal, overlap the Material Plane and the Inner Planes, so that every location on those planes has a corresponding location on the Ethereal Plane. (PHB, p. 301)

Does this make possible the ability of having one’s familiar become an ethereal traveler?