What temperature is too low to grow a pineapple plant outside?
Different plants require different temperatures. As to your pineapple, a temperature between 65 - 85 degrees F is optimal. It's a tropical plant and needs a warm, protected environment. Here's an article that will tell you more:
https://www.gardeningknowhow.com/edible/fruits/pineapples/care-of-pineapple-plants.htm
Ask previously about this & have taken steps to fix soil ph but my question is should I remove the brown leaves
Once they are completely dead, yes. Until then, they are still completing photosynthesis. If you choose to remove dead portions, stop before any green plant material to avoid spreading disease.
My friend cuts the top of the pineapple before it is ripe; she says it makes it sweeter.
One of the amazing things about gardening, you can always learn tips from another gardener, however, I couldn't find any source that suggested this technique.
Here is info on harvesting:
https://www.gardeningknowhow.com/edible/fruits/pineapples/picking-pineapple-fruits.htm
I started a pineapple plant from a top about a year and a half ago and it has finally grown to about 18 inches tall. Can/should I transfer it to the flower bed?
Pineapples are hardy in zone 10 and up. Since you are in zone 9, it will not survive the winter in your area. I would keep it in container. Here is an article that will help:
https://www.gardeningknowhow.com/edible/fruits/pineapples/care-of-pineapple-plants.htm
I feel that I have a better location for my pineapples and I do realize I will have to cover them when the temperature gets too cold.
Here is an article that provides tips on transplanting. They don't have a very big root system so it should be easy to get all the rootball. Also, they don't tolerate frost, and I notice that even in zone 9, you can get below freezing. So, if you aren't bringing them indoors for the winter you will need to take extra precautions to keep them from freezing.
https://www.gardeningknowhow.com/plant-problems/environmental/protecting-plants-winter.htm
https://www.gardeningknowhow.com/edible/fruits/pineapples/care-of-pineapple-plants.htm
When I cut the pineapple from the stem do I need to trim the stem back or treat the stem with something to stop from rotting
Experts say you should leave an inch of stem on the plant. I'm not seeing any research that suggest the remaining stem should be treated with anything. Unless you see signs of problems with the plant, it should dry up and be fine. On the other hand, if the remaining stem shows signs of rot, you may have other problems. Here are links to a couple of articles that should help:
https://www.gardeningknowhow.com/edible/fruits/pineapples/picking-pineapple-fruits.htm
https://www.gardeningknowhow.com/edible/fruits/pineapples/dealing-with-pineapple-problems.htm
My Pineapple plant has grown a pineapple already but now has two children growning from itself. Do i cut out the two plants to replant or leave it alone? I dont want to hurt the plants but i dont know what to do at this point.
Those can be repotted when the mother plant begins to die back. The mother plant only fruits once, then will fade away. The new sprouts will grow and produce fruit.
https://www.gardeningknowhow.com/edible/fruits/pineapples/pineapple-plant-fruiting.htm