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Use image hosting sites like PRTSCR.com and post the link after uploading.
I think that it depends on distance, further you take flag more points you get. Keep in mind this is not official data, This is all personal experience and opinion. BTW killing that was holding you flag gives you 20 points in score. I think 10 for kill and 10 for flag.
I think that 4+ RAM on your computer would be fine. Processor can be somewhere 2.2GHZ. 2GB of graphics should be fine. Good internet connection is also a key to a smoother gameplay. 
I think there are two reasons for that, depends on what do you mean.

1. if you are low rank and you meet for example mamoth m3 in the battle and you have smoky m1, it will be almost useless to kill that strong enemy.

2. It may be lag. From my personal experience I have simillar problem when using vulcan. My friends told me once.. Hey man your vulcan is not effecting when you shoot, I looked at the fps and ping where fps was pretty low and png was high.

Hope this helps.
I changed name on my second account. Following information is from tanki online support team. I hope this helps.

Changing your nickname is a paid service which costs 100 000 crystals. If you agree, this amount of crystals will be deducted from your account.

To change the account nickname, we need to verify that you are its real owner. Please send us an email, containing the following information.

1. Your nickname in the game.
2. Have you ever invested real money in the game, if so, specify the dates of payments and state the method of payment (if using SMS, write your phone number).
3. Are you someone's referral? (referrals are players that joined the game by clicking on a banner or a link). If so then enter the nickname of your referrer (the person who invited you to the game).
4. Which e-mail address your account was linked to after the registration?
5. Which serious bans / punishment were on your account?
6. The last time you entered the game (date).
7. Where do you play from (country, region, city)?

Please provide a screenshot containing your external IP address from the page http://whatismyipaddress.com and place it on a free image hosting website such as: http://imageshack.us/

8. What is the last hull purchased on your account?
9. What is the last gun purchased on your account?
10. You need to send us a new nickname for your account, which is not occupied by another player and does not break the rules of the game. The maximum length of nickname is 20 symbols. You can learn how to check nickname availability here:http://en.tankiforum.com/index.php?showtopic=168476

You can find information on how to make a screenshot and upload it here:

http://en.tankiforum.com/index.php?showtopic=163430

The more information you give and the sooner you do it, the faster we will be able to help you
Mostly it's on special days, like valentines day, christmas and so on. Sometimes there are random sales. Tanki online normally gives information about sales day before, if the sales are coming on Monday for example there is a good chance that information about sale are given in the V-log of the last week.
From personal experience you get crystals randomly, somewhere about once in a month. Sometimes 2 times in month. But if you watch last V-Log tanki online is planning to add something called ''DAILY MISSIONS'' where you have to complete missons for daily rewards. For example kill 10 vikings or capture 30 flags.