A greenhouse in your climate would boil anything inside it I should think. I reckon you need to be looking at shade rather than a greenhouse.

Can you describe your seed sowing methods? It sounds as if something is going wrong very early on. There may also be a problem with the seed if its from your own plants. Are you sure it's been pollinated? And are you sure it's ripe?

Basically i take the seeds for storage, just before the plant flowers.
When the seed looks like this
http://freeimagescollection.com/images/flowers-closeup/tulsi-flower-closeup-f5.jpg
http://upload.wikimedia.org/wikipedia/commons/8/83/Tulsi-flower.JPG

I remove all these things from the stem and put in the soil for potting. (I assume these are seeds).

Then i place them on soil, and place a very thin layer of soil above it. (I have tried thicker layers).
The soil gets sunlight - same amount as the plant does, hot temperatures and good humidity, with no freezing conditions at night.
I mist the soil everyday (And i have also tried covering the pot with plastic to avoid moisture escape in another try).
Honestly by doing this, my seeds never managed to germinate.

In another different story, someone else had potted seeds. Many of them germinated and few of them died.
Its been like 4 months since they germinated and their height is no more than than 1-2 cm.
They are just living with 2 TINY leaves from months. no growth.
i still mist them everyday.

I have trouble with many things, but not basil. I'm in a 4 season climate, cold snow winters and plant my basil when the temps are no longer cold, BUT, my basil bed is different than others.
It is raised and has lots of clean sand mixed into the soil. In my climate it needs drainage and not that much water. I've never misted. My basil bed is 2.5 x 5ft. Often 5or6 varieties. It grows quick and thick without effort. It likes drainage and not much water, at least in my climate.
Maybe try a small section in your plot of early sun using an elevated raised bed. Sandy soil. Just mix a bag of sand into your soil.
I have a full tray of starts that also are full and thick without much effort. (kinda dumb as i have no place to put them being a month from setting in the garden).
Direct seeding on the sandy damp soil, then a dusting of clean peat or light soil is all i need.
I don't usually gain much by staring seeds early.
Also, do not feed or fertilize. Try it bare and existing soil only. Basil is a bit of a weedy thing and does not want much attention. Just drainage, (sand), and a bit of damp once a week.
-i do get hot, very hot weather in july...95+ but cooler nights.

Basically i take the seeds for storage, just before the plant flowers.

Then it sounds as if you aren't harvesting seeds. The flowers have to bloom, be pollinated, and die before mature, viable seeds can be harvested. Agree with sleevendog above - basil is easy to grow. But first you have to have actual viable seeds. Then you provide it the proper growing conditions - small containers with shallow soil, proper amounts of water (no misting), etc.

4 months since they germinated and their height is no more than than 1-2 cm.
They are just living with 2 TINY leaves from months. no growth.
i still mist them everyday.

That is caused by the potting mix you are using and the way you are watering them. Daily misting is one of the best ways there is to stunt growth and kill plants. Water the soil when it is dry, not the plant.

Dave

ok so after i harvest the seeds, how much should i pot in a small starter pot?

any rule of thumb?
because overcrowding will not allow other seedlings to grow i guess...
and potting a single seed wont do the job either i think...

is region 1 shown in below picture good for starting seeds?
http://creativejewishmom.typepad.com/.a/6a011570601a80970b0154353fb0a0970c-800wi

That bit of plastic bottle is too small imo. Get a proper pot or container like a yoghurt pot, maybe .25l. It MUST have drainage holes. Just fill it with seed sowing medium. Take a small pinch of seed between finger and thumb and sprinkle over the surface of the medium. Water from the bottom until it looks wet on the surface. That will be enough to bed in the seeds. I don't find any need to cover the seed. Put cling film over the pot and place somewhere warm and light. The seedlings should show in a few days to a week. Take off the film and remove from the bottom heat. Keep in a warm light place. When the seedlings are 2 - 3 cm tall and have at least 1 set of true leaves transplant to separate pots, or, and this is what I do, don't thin and grow them dense. Because, in my climate basil doesn't do that well because of lack of heat so the plants don't get very large. In your climate they may get big and need their own pots or in-ground planting.

Why not read through the FAQs here? They cover all the basics on how to grow anything from seed.

And surely you can find better containers to use than the plastic bottle you linked above.

But first you have to have mature, viable seeds. That means buying them or harvesting them only AFTER the plant blooms and then the blooms turn brown and dry on the plants.

Dave

Here is a link that might be useful: FAQs- How to grow from seed