Can you benefit from the Dueling fighting style for one weapon, then draw a second weapon as part of Extra Attack to qualify for Two-Weapon Fighting?

Say a Champion fighter has the "Two-Weapon Fighting" fighting style and the "Dual Wielder" feat. At 10th level, they pick up "Dueling" (+2 to damage rolls when wielding a single one-handed melee weapon) for their 2nd fighting style. Since they’re 10th-level, their Extra Attack feature lets them make 2 attacks as part of the Attack action.

Can they have one weapon drawn for their first attack, to benefit from Dueling – and only then draw another weapon for their second attack in the Attack action, in order to meet the requirement for Two-Weapon Fighting (and thus deliver another attack with their bonus action)?

Is it possible to qualify for a Greater Dragonmark in E6?

I’m considering running an E6 game in Eberron, and I’m curious if there is some way to qualify for the Greater Dragonmark feat.

Skill Beyond Your Years and Primary Contact can let me reach 12 ranks in a single skill, but the feat requires 12 ranks in two different skills. I’ll likely houserule it, should there not be a way to reach it, but I’m curious if anyone knows of another way to reach 12 ranks in a skill in E6 (or some other way to acquire the Greater Dragonmark feat).

Do Dvati qualify for Multiweapon Fighting?

They have 4 arms between them. A Dvati ‘character’ taking the feat has 4 arms. OTOH, of course, if you look at them as separate creatures, neither qualifies. …I’m leaning towards the first interpretation, honestly, but what are your thoughts?

“Would this actually benefit them, anyway?” I hear you asking. Actually, yes. If the ‘main hand’ attack is, for instance, an unarmed strike with the leg, both hands a free for extra attacks courtesy of Multiweapon Fighting.

When substituting one ability for another on a skill check which kind of check does it qualify as?

The Unearthed Arcana Monk tradition Way of the Astral Self has the following ability (page 2 of the PDF):

Arms of the Astral Self

You can use your Wisdom modifier in place of your Strength modifier when making Strength checks and Strength saving throws.

Imagine such a monk took 1 level dip into Barbarian and picked up that class’s rage ability which includes:

You have advantage on all Strength checks and Strength saving throws.

If the monk goes to make a strength check (say, a grapple check), does the monk have advantage on the check because it counts as a strength check (but she’s using her wisdom modifier)?

Or does she roll a normal check with her wisdom modifier because it’s now a wisdom check, as determined by the fact that she’s using wisdom for the check, not strength?

Does a race that is a sub-variant of another one qualify for feats restricted to members of that race?

Does a character being a race that is described as a sub-variant of another – for example, Svirfneblin to Gnome – qualify said character to take feats that are restricted to members of the super-race (for want of a better term) – for example, Earth Child Style – due to sharing a sub-type?

Does a Sun Soul monk qualify for the Spell Sniper feat at level 4?

The Way of the Sun Soul monk (Xanathar’s Guide to Everything, p. 35) gets the Radiant Sun Bolt feature at 3rd level:

You gain a new attack option that you can use with the Attack action. This special attack is a ranged spell attack with a range of 30 feet.

They also get the Searing Arc Strike feature at 6th level:

Immediately after you take the Attack action on your turn, you can spend 2 ki points to cast the burning hands spell as a bonus action.

The Spell Sniper feat (PHB, p. 170) has the following prerequisite:

Prerequisite: The ability to cast at least one spell

I was recently designing a Shadar-kai Monk who would take the Way of the Sun Soul archetype (ironic, I know). In the process, I began thinking about how he would benefit enormously from the Spell Sniper feat (increase his range from 30 to 60 ft). I then noticed the prerequisite on the feat and began thinking…

Does a ranged spell attack count as casting a spell (thus allowing the Sun Soul to pick up Spell Sniper at level 4)?

Or does the Sun Soul have to wait until he gains Searing Arc Strike at level 6 to qualify for Spell Sniper for his level 8 feat?

What happens if you no longer qualify for a Racial Substitution Level?

Racial Emulation is a lovely little feat that lets changelings (humanoid shapeshifters) count as the race they have changed into for most things, including taking racial substitution levels for that race. (Another way to do this would be polymorph shenanigans).

What happens when they then change to a different race?

Does this fall under the same banner as prestige classes, where it’s generally accepted (if still slightly controversial) that you only need to meet the prerequisites for the first level unless there’s a specific rule to the contrary? (Although the way racial substitution level requirements are phrased, you’d still need to be the correct race at the time you took each RSL, not just the first one.)

Or is that not the case, and you revert back to the default class features when not in the correct form? Or get no features at all for that level until you’re back in the right shape, because you don’t qualify for the RSL features and never took the default features?