How do Dimension Door and Find Steed / Find Greater Steed interact?

Find Steed has this sentence (and Find Greater Steed has an equivalent one):

While mounted on your steed, you can make any spell you cast that targets only you also target your steed.

Dimension Door has this restriction with regard to taking someone else with you, where the restriction is size is the important bit:

You can also bring one willing creature of your size or smaller who is carrying gear up to its carrying capacity.

Take a medium-sized character (such as a Bard with Magical Secrets) mounted on a summoned a large mount (such as a warhorse), casting Dimension Door:

Is it possible to make Dimension Door affect this mount?

Can the Dimension Dervish chain be use in conjunction with combat, teamwork feats?

Can I string the Dimensional Agility Feat chain (specifically, Dimensional Savant) and Precise Strike feat together? As I read it since I can flank with myself as an ally doesn’t the feat bonus apply as well?

Precise Strike:

Whenever you and an ally who also has this feat are flanking the same the creature, you deal an additional 1d6 points of precision damage with each successful melee attack. This bonus damage stacks with other sources of precision damage, such as sneak attack. This bonus damage is not multiplied on a critical hit.

Dimensional Agility:

While using the Dimensional Dervish feat, you provide flanking from all squares you attack from. Flanking starts from the moment you make an attack until the start of your next turn. You can effectively flank with yourself and with multiple allies when using this feat.

Can the pocket dimension created by the mirror of life trapping be returned to by using the Gate spelll?

A wizard needs a few decades to think over a problem, and decides to do so in his mirror of life trapping to prevent himself from aging. He packs a bag full of writing supplies and a 5000gp diamond, and has a servant activate the mirror to trap the wizard inside. After a few years have past, the wizard realizes he misses his liquor cabinet, and casts Gate to return to his study. After grabbing a couple bottles and regaining his 9th level spell slot (he took too long and the gate had run its duration), he wishes to return to the mirror. Can the wizard recast gate and step back into the mirror, or must he return to the mirror by his servant reactivating the mirror? Does the extra dimensional cell remain in existence when the wizard leaves it, or collapse until the cell is refilled? What if the wizard leaves his notes, are they ejected when the wizard leaves?

If applicable, what other pocket dimension can or cannot be returned too in this way?

How close to you does your Familiar have to be for you to be able to dismiss it into its pocket dimension?

How close to you does your Familiar have to be for you to be able to dismiss it into its pocket dimension?

Within 30′, to match the area you can resummon it into? Within voice range? Within 100′, which is its telepathic communication range? Within 120′ if you use the Message cantrip to make the command? Within any distance on the same plane, if you have Voice of the Chain Master? Within any distance on the same plane, regardless? Within any distance on any plane, if you cast Sending to make the command? Anywhere in the multiverse? The Find Familiar spell does not say.

Does casting dimension door or compulsion with the magic dagger Bookmark expend your bonus action and your action?

From Tomb of Annihilation, the description of the magic dagger Bookmark says:

While you have the dagger drawn, you can use a bonus action to activate one of the following properties:

  • Cast dimension door from the dagger. Once this property is used, it can’t be used again until the next dawn.
  • Cast compulsion (save DC 15) from the dagger. The range of the spell increases to 90 feet, but it targets only spiders that are beasts. Once this property is used, it can’t be used again until the next dawn.

Both dimension door and compulsion have a casting time of one action.

Does using a bonus action to activate one of these properties enable you to then use your action cast one of those spells, or does the Bookmark change the casting time of those spells to 1 bonus action?

Does Dimension Door up, then Feather Fall work as I expect?

My character wants to impress a person by teleporting 500′ up with Dimension Door together with them, then casting feather fall to spend the next almost a minute (500′ / 60′ = landing on 9th round) admiring the scenery and conversing privately.

Does this work as expected?

My own thoughts:

Dimension Door up should be unproblematic (it takes a special kind of DM to roll for bird impact here).

My main worry is, does the Feather Fall, cast as reaction when falling, activate immediately at 500′ giving the full “flight time”.

Then landing should again be problem-free, right?

Any hazards I am not aware of, assuming there are no hostiles shooting at the falling characters?

Dimension Leap with A Held Rope

My Bard is holding one end of a 100′ rope in his hand. The other end of the rope is in a row-boat, either tied to the boat or held by another character in the boat.

The Bard casts Dimension Leap to teleport 90′ away.

What happens to the rope? We are trying to create a tether to attach a row boat to a ship, to be able to pull the row boat to the ship.

In a data warehouse, should a measure be based on a fact or a dimension?

Let’s say there is a data warehouse created from a shop data. A fact is a single purchase of a product. There is a dimension that describes a customer.

There is a need to create a measure that stores a number of distinct customers. Can this measure be created based on customer identifier in the dimension table, or it needs to be fact table? In which cases one or the other solution is better?

Below I post a visualization based on an AdventureWorks2016 database:

Data warehouse example visualization based on a AdventureWorks2016 database.