How to close the position in futures

I am new to Futures & before starting trading in Futures I want to clear some doubts.
In india futures are settled in cash only not a delivery is made, I think i am correct.
But i want to know how to end the future position ,

suppose i take long position in future at one day & on the same day if i take short position then can i get out of both the positions having no any liability & i will get or have to pay the difference amount OR

suppose one day ABB's future is at 3500 & its spot price is 3485 then that day if I have short ABB future @ 3500 & wants to close the position then what should i do whether taking reverse position in future or any other else

becoz my understanding is if we donot take reverse position then on delivery date difference between spot price & future price is calculated & crediteded or debited Finally
if I want the same thing on the day when i will short the ABB future @ 3500 fthen whether FINAL SETTLEMENT can be happened without taking reverse position.

In short what are the ways to close the position in Futures
I) reverse position???
II) Any else before maturity date

Also I want to ask that can I extend my one month future contract to next month or not

I know that my doubts are very silly & negligible , but if you clear that
it will help me more to study more about futures

I request all Sr & Co members to clear my doubts

Let me make things clear with an example.
ABB Spot is 3485
ABB Nov Futures are at 3500
You short ABB Nov Futures at 3500
Now, ABB drops the same day to 3385 and futures are at 3400.
You can take profits by buying the ABB futures at 3400. You lock in the 100 point gain, and have no further obligation. If you think ABB is going to drop further, dont buy it back.
On expiry day, ABB is at 3300, and the futures are at 3303. You can buy back the Nov futures at 3303, or let it expire at 3300 (that is if the last half an hour average stays at 3300).
If you feel ABB can fall still further, you can carry your position forward by buying back the Nov futures and selling the Dec futures.

Hope this answers your query.

Thanks a lot , sir
It cleared my all doubts about closing of position in futures .
I am really thankful to u, for driving ur attentation & sparing some time for this
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hi,
i want understand the meaning of "Open Interest" . Can u please send me an email on [email protected] Thanks.
subhadin

Refer to these threads for prior discussions on Open Interest
http://www.traderji.com/futures/4592-intraday-openinterest-nifty-future-2.html
http://www.traderji.com/derivatives/8351-interpreting-open-interest-volumes.html