Can the current HP of a damaged Construct/Simulacrum be increased by spells or class features that don't specify "Healing"?

Question

As of the 2018 PHB errata, the creature generated by Simulacrum is a construct. Constructs cannot be healed by many spells or features, such as Cure Wounds or a Paladin's Lay on Hands (that specifically state that their healing cannot be applied to Constructs/Undead). As the Simulacrum spell lays out a costly HP-restoration method for it "using rare herbs and minerals worth 100 gp per hit point it regains", it seems that the RAI (Rules As Intended) was for that method to be the only viable way to regain hit points.

This leads into two questions:

1. Fighter has the Second Wind feature, that allows it to use a Bonus Action to "regain hit points equal to 1d10 + your fighter level.". Since it's using the same 'regain' word, would this Bonus Action allow a Construct-type creature with the appropriate levels and/or a Simulacrum to regain hit points?

This one is a little iffy in my opinion, as the 'regain' word is specifically called out in the text of Simulacrum.

2. Spells such as Aid and Heroes' Feast exist, that respectively have the text of "Each target's hit point maximum and current hit points increase by 5 for the duration" and "Its hit point maximum also increases by 2d10, and it gains the same number of hit points". Since both of these spells "increase" HP or cause the creature to "gain" HP, do those work on Construct-type creatures and/or on a Simulacrum?

This one seems more clear-cut. Increasing HP / Gaining HP isn't specifically "healing" damage or "regaining" damage. When Aid or Heroes' Feast expire, they only reduce current hit points if they are above your maximum hit points, so I'd understand it that a cast of a 2nd-level Aid on a Construct/Simulacrum with... say, 10/40 HP, would increase that to 15/45 HP, and upon expiry of Aid would then be at 15/40 HP.

Before I posted, I did find 'similar' questions, but they seem to focus on "Healing", or be treating the HP of Aid as separate/"healable" HP.

Answer 1

Purely rules-as-written yes, but designer intent is that you only can regain hit points by the alchemical procedure

There is this answer, which argues that since simulacrum's text explicitly states

If the simulacrum is damaged, you can repair it in an alchemical laboratory, using rare herbs and minerals worth 100 gp per hit point it regains.

Repairing is the only way to undo damage and so it cannot be healed by healing magic. The same logic would apply to hit points from Second Wind.

There also is the argument that the alchemical procedure would be meaningless if there were other significantly cheaper and simpler repeatable methods of healing the simulacrum.

However, the text of simulacrum does not actually say so. So strictly as written, other features that add back hit points would work.

Increasing hp maximum

Increasing the hit point maximum is not repairing, these points can come on top of a simulacrum at full health, one that is not damaged, and by that logic the hit points that come with it would also not count as repairs.

If the simulacrum was already damaged, the added hit point that match the maximum increase would partially or fully be used to offset existing damage; however, as the hit points are again lost along with the increased maximum when the spell's duration ends, they are not really repairing a damaged simulacrum even in that case. So even considering the designer intent discussions below, these transient hit points should be OK.

Designer intent: Regaining hit points

There are multiple tweets by Jeremy Crawford, that the alchemical procedure is the only way to have the simulacrum regain hit points, and this is not a case where he is inconsistent. There is this tweet:

Q: Can the creature created by Simulacrum be healed by spells?

A: To restore hit points to a simulacrum, you must use the costly alchemical procedure mentioned in the spell.

He does not make any exception, not even for Wish. Gandalfmeansme found yet another tweet asking about hit dice explicitly where Jeremy again confirms:

Q: Is the intent of Simulacrum that it can be healed through magic,hit die/resting,or ONLY through the alchemical process?

A: The intent is that the simulacrum (PH, 276) can be healed only by the alchemical process.

Designer intent: use features once and then nevermore

Additional tweets by Jeremy state that simulacrum cannot regain spent features.

The creation is meant to be unable to regain use of any of its features that it expends (RAI)

In a followup he suggested there may be errata to this effect in the future and that

A simulacrum is meant to lose efficacy over time, essentially running out of juice, until only at-will abilities remain.

You could argue that Second Wind is such a not-at-will ability, and thereby it should be possible to use it least once.

Conclusion

Jeremy's tweets are not official any more. You can of course decide to ignore his missives about designer intent, and rely only on what is written in the official rules.

Consider that Simulacrum is widely seen as a spell that is already broken, effectively doubling your spell slots and actions and providing unlimited ritual casting. I think it is wise to employ any reasonable restrictions.

You should clarify how this is handled with your DM.

Answer 2

Yes, UNO

The Monster Manual (p.5) says of Monster Types:

A monster's type speaks to its fundamental nature. Certain spells, magic items, class features, and other effects in the game interact in special ways with creatures of a particular type.

However, if the "spells, magic items, class features, and other effects" don't say that they "interact in special ways" with constructs, then there are no special rules that they don't.

So unless the rules say a specific construct can't be healed (which most don't), then they can be provided the method itself doesn't prohibit it. Similarly, while the simulacrum provides a specific repair method, it doesn't prohibit other methods.

1. Second Wind has no special rules about not affecting constricts or simulacrum, so it's good to go.
2. Neither Aid nor Hero's Feast states that they don't work on constructs (or undead) or simulacrum, so they do.