1 - How much water do you use daily?
I only read a few comments before I decided to respond... None of us can tell you an exact number to what you are searching for. Growing cannabis has too many variables to be 100% correct so let me give you a guide instead.
When you water wait till the plant begins to show signs of wilting before watering. Roots need three things, water, oxegen, and food. If you over water or under water you will see signs of potential root rot, nats, slowed or stopped growth just for starters. It is important to recognize your plants reasons for crying just like a baby that can not talk.
When you grow keep a journal. The next time around you will be able to be faster at detecting an issue and you will have an idea based off of your individual variables. Heat, humidity, plant size, pot size, medium, and much more come into account when tracking the amount of water being consumed in a soil grow.
What I suggest is learning as much as you can growing in a soil medium because you have more time to correct the issues then change mediums as soon as possible and introduce a drip system or dwc.

2 - At the stage of flowering, is it possible to clone the plant?
If you take a clone in the first two weeks of your flowering phase ( also known as the transition period,) you will have them back in veg in less than a week. If not cut your clones before these weeks, if not your only going to loose product when your cutting off your colas... It's worthless doing that.
3 - How much Kwh for each stage?
Again, variables come into play. Signs of stress to look for are burned tips on the fan leaves and bear clawing where the tips curl down and in. I usually run about 600watts starting at week four on my clones when they first go into veg. I bump up 200 watts each week till I hit my 1200 watts and then flip to flower. I have LEDs with both the blue spectrum and red spectrum... I run both spectrums for both weeks of transition and drop to the full red spectrum in the third week or first week of flower (if you keep your transition period seperate of flower).

I hope that helps. Any more info needed hit me up any time... I don't know everything by any means but what I do know, I know the reason in why what I do works. Which is more important in my oppinion. especially when your investing so much money into your grow. So much faulty information out there.