Will it help to cut it back and bring inside?
It is likely that it will survive. It will likely, also, stay dormant until Spring. Once it comes time for it to come back out, give it a light pruning to take off any dead material, and it should spring right back to life.
This article will help: https://www.gardeningknowhow.com/ornamental/vines/mandevilla/winterizing-mandevillas.htm
I brought the plant indoors for the winter months.
Yes you can easily propagate this plant from cuttings.
This link will help you, it is referencing the Mandevilla but the procedure is exactly the same for your plant.
at night can thet tolerate and still remain healthy or should I bring them in garage at night??.
I should not fall below 65 at night. Any lower than this, and it will risk the health of the plant.
Here is an article that will help you with their care:
NES WILL IT KILL THE PLANT OR DETER FROM FLOWERING? I JUST THOUGHT IT FUN TO SEE IF I COULD WINTER THIS CONSTANT BLOOMER...IT IS SO HEALTHY, BUT THESE LITTLE VINES HAVE ENTANGLED EVERYTHING. WHEN OUTSIDE ALL LAST SUMMER IT JUST BLOOMED BEAUTIFUL FLOWERS, NO VINES APPEARED. HOPING YOU WILL SAY I CAN CUT THEM AND NOT KILL IT, AS I WANT TO PUT IT OUTSIDE AGAIN. THANK YOU.
You can cut it back before you put it outside.
Here's an article that will help you with your plant:
I have a diplademia plant that I would like to treat as a vine.
Diplademia's growth pattern is to hang and become bushy, but it's not necessarily a climber like Mandevilla.
This article will help: https://www.gardeningknowhow.com/ornamental/vines/mandevilla/growing-a-dipladenia.htm
How often to water? distance of growing light from plants?
You can set the time, anywhere, between 12 and 18 hours of light. 12 hours a day will save energy.
As far as how high to hang the light- That depends on what light source you choose. Generally, the light of your choice will have hanging instructions and you can adjust to the plants needs as you see fit. Unfortunately, this answer isn't straight forward.
Watering should occur as the soil dries, thoroughly, down to about 2 or 3 inches. Once it is dry down to that depth, you can water until it starts to drip out of the drainage holes. Make sure to discard all extra water from the saucer.
These articles will help:
I live in South Africa and always have 3 dipladenias in large pots on my terrace. While 2 flourish the third often shrivels and dies. Do they only have a certain lifespan?
My research showed they are perennial in warm climates such as yours. So, no, I wouldn't say they had a short lifespan like annuals. Perhaps the third plant succumbed to disease or insect invasion. Sometimes identical plants only a foot apart will perform differently. Does the third one get more shade perhaps than the others? Does it have a larger pot that may be causing more moisture retention leading to root rot?
Here is care information.