i cashed in (almost) all my United files for 2 one-way LAX to Europe (we're meeting up with a cruise)
it was 40,000 miles per person ... is this the best rate and i don't need to keep checking for a price drop?
(i know Delta rates can swing up or down)

Like Delta, United uses dynamic award pricing. I think 40k miles LA to Europe is pretty decent for Economy. For Premium Plus it would be a no brainer. I don't think you'll see Polaris awards on this route for less than 80k or so.

There's no kind of partnership anything with LATAM for UA MP, is that right?

Copa.

In a couple of weeks, I'll be flying a three-leg trip from EU to US via FRA and IAD (FRA-IAD-US on UA flights) in Polaris.

It's my first time on UA business class.
1) What lounge do you recommend in FRA?
2) What amenities need to be asked for on the flight FRA-IAD (e.g. mattress pad, noise cancelling headphones, etc.)?
3) Anything that you recommend for a nicer experience?
4) I have a 3.5 hour connection at IAD. I'm planning to visit the Polaris Lounge. I understand there's a dining room - is this an extra fee service?

Unless you have *G status, you can access any of the LH Business Class lounges, just pick the one closes to your depart flight gate.
headphones and amenity kit plus pillow and blanket will be already at your seat. The flight will not have PJs.
5 days prior to travel you will be able to select your departure meal. If available, odd window seats are the most private.
No extra fee.

Traveling mid-April, 2 people on an open jaw RT: IAD>ZRH, then returning CDG>IAD. Outbound purchased in Polaris, return purchased in Premium Plus. Currently holding an MUA into Polaris on the return (cost: 20K miles +$425).

Prices since purchase January 1 have been bouncing around a lot, first up as high as $1750pp more than I paid, today back down within $150pp of my purchase price.

1. If the price for the entire itinerary drops significantly below my purchase price, can I cancel and rebook an intl open jaw? If so, would cancel/rebook be any cleaner than changing and then changing back to the original itinerary?
2. If it is possible to cancel/rebook, or change and then change back, what happens to my MUA? Do I lose the miles and cash?

TIA.

I'm traveling with 4 companions HNL-LAX this March. I'd like to waitlist myself only for an upgrade on both the outbound and inbound. If I do get upgraded, I'm pretty sure my PNR will be split, does that mean they will have to pay the luggage fees? (I'm currently gold, so I think my companions get waived luggage fees for up to two luggages at 70lbs each).

You have to split the PNR just to apply the upgrade if you are only applying for yourself.

Baggage is YMMV, technically yes they'd have to pay although checking in together with you, most agents will waive it (or have in the past).

Clearing the waitlist on LAX-HNL as a Gold is a doubtful proposition, to say the least.

When I book a basic economy seat on United as a Star Alliance Gold, the website says I get 2x23kg baggage allowance. Is this correct or just a glitch on the website?

you get a +1 as a *G. So it will depend a bit on the route and whether this a checked bag allowance. EWR-BOS you would get 1 checked bag

Does the boarding door always have to be closed between deboarding the inbound and boarding the outbound?

Trying to figure out how thin I can slice the salami here with waiting to go to the gate 😅

No. (ETA: It is common for the door to the jetway — not the aircraft’s boarding door — to be closed, if that’s what you’re asking. Even that — I’m not sure it’s strictly required. The jetway door has to be closed when it’s unattended, but I’ve seen boarding commence without the gate agent ever needing to leave the front of the doorway. Thinking back on it, they may close it just long enough to reopen it with their code, to ensure that the entry log is set up properly, but you’re talking a few seconds at most here.

You are required to be at the gate at T-15 for domestic departures or T-30 for international departures; I think there are some exceptions in the North Pacific where you need to arrive a little earlier.

What you really seem to be asking about is “when will they start boarding,” which has a ton of variables, most of which won’t be known to the traveler.

Yeah pretty much, I am happy to not go to the gate until boarding starts. Usually I can rely on the push notification or text, but sometimes I can see the gate from a lounge or cafe/bar/etc, and that gives me more confidence I won't miss the boat. I think I always see them close the boarding door for a few minutes after the cleaners get off, then come back out and start boarding some time soon after. I'd like to use that as my cue to get up and head over!

If it wasn�t apparent, this really only applies when things are running behind schedule. 🫠