I have currently grown two orange/tangerine seeds in a 6" pot into small sprouts about 2", but it's been about 2 months and they have basically stopped growing (but they are still alive and look healthy.) What can I do to get them more light and warmth even though it's winter? Will regular lights work as well as sunlight for photosynthesis or is it the wrong wavelength? I don't want to buy any specialized lamps or bulbs for them.

What should I do to keep them warm? Will keeping them in an airtight container help keep heat in? Should I blow in it to add moisture and CO2?

I am also planning on growing a mango pit that I got out of a mango from the grocery store, but I think I will wait for spring. Any tips for that too?

Mainly I just want to know if it's possible to have warm-climate plants thrive in a house at 20 degrees C, or should I basically just rip them out and wait until spring?

When the oranges came up they had 2 shoots and I cut one off... is that y they stop growin
The little sprouts are just one stem with two leaves at the top, and the stem looks like a little stub is forming and extending between the leaves.

I ran out of room at the bottom of my question to really mention properly that the plants both came up with two sprouts, and I cut one off of each. I thought they were twins and it was just a freak of nature, but now that they stopped growing I wonder if that is why.

Citrus needs full spectrum light and citrus fertilizers to thrive. Since your plants are young, they are tender and need specialized TLC. You need to keep them warm: Hang a bare light bulb close to the soil to warm it. They need full spectrum color waves for at least 8 hours a day. You can purchase a full spectrum light bulb from Home Depot or Lowe's and put it on a timer. They need humidity which can be accomplished by placing the pots into a pan with stones. Water only from the bottom to help the roots reach and grow. Use a half strength water soluble fertilizer until the trees are freely leafing and branching. Then switch to a specialized granular citrus fertilizer. Be very careful not to overwater and don't pinch off or cut anything until the trunk of the trees are at least the thickness of a pencil!! The tender shoots may not be able to handle the stress..

Try a very large size terrarium with stones under the soil, if it gets too cold put a small size light bulb for warmth. That will not give them enough light for growing citrus though.
You definitely need to buy a grow light bulb. They work in regular drop cords, about $15 for bulb and cord.

You need to not only provide them with light, but a moist environment as well. Put a large dish full of rocks that you can fill with water at the base of the plants; this will allow the water to evaporate and rise up to keep the foliage moist. Also, misting the leaves often will help.

When I am starting my seeds indoors, I just use a regular shop light fixture with aquarium bulbs. They aren't that expensive (I think 5 bucks for the fixture and maybe 12 for the bulbs?) and the plants love it. I don't think your tropicals would require anything different; however I'm not an expert!

I don't know how successful you could be at getting them to bear fruit, at least during the time they are indoors.

Good luck!