Alright, I have a lot to cover here and not a lot of time so I am just going to dive in and I apologize in advance if I come off terse
In some cases yes in others no. There are at least 4 distinct clones of this species in cultivation. One clone (var. forgettiana) is very free blooming and does not require a rest phase (I do not like the term dormancy cause the plants are never in a state of inactive growth, just slowed growth.) Two of the remaining clones do require this rest phase to consistently flower and the last one is squirrelly, behaving differently in different peoples collections.The dormancy is required for flowers.
This will not be much of a problemThe only problem I see you having with growing a Heli with U. longifolia is that the U. longifolia will take over and fill the pot. This may or may not have an impact on the Heli.
If the goal is to grow them together I doubt this will be a problem eitherYou also may never be able to completely separate the Utric from the Heli when it's time to repot.
As I said above, this depends on the clone.WHAT? It is absolutely not necessary for flowers. At least for my clone.
Just an FYI, plants growing in Heli pitchers are significantly weaker than those under other conditions. Seems something in the Heli is a bit detrimentalBut U. nelumbifolia goes really well with helis. I've actually got one with it's tendrils in a helis pitchers, without my help! The tendrils are starting new plants in the heli.. kinda cool.
Remember that U. longifolia is wholly unrelated to the rest of the "macro" Utrics. What it can tolerate and what the Orchidioides and Iperua can tolerate are not the same thing. The only Iperua that is as tolerant as longifolia is nephropylla.Many people are just realizing some of these macro utrics can take a lot wetter conditions than people generally expect.
Here's my proof:
Not quelchii, it really cannot tolerate overly wet conditions. The bromeliad associated Utrics are mostly humbo and nelumbi though reni have also been found in them on rare occasionsI believe that U. humboltii and U. quelchii(?) are the only Utrics that I have made a positive connection to Helis in the wild.
And, just a quick answer for you. Atlanta Botanical has U. longi growing in among the Helies in the highland display greenhouse so you should be fine having the two together in your set up.