Habrokvest in honor of the 20th anniversary of the Mail.Ru Group - 20 puzzles

Hello! Perhaps you remember the puzzle quests that I did in 2010 and 2016. Version 2016 is still being held, but it is time to update the tasks. We took into account the wishes of the last game: now there will be more prizes, and it will be possible to pass at a quiet pace until the end of the week. And we are rolling out the new version in honor of the birthday of the company - Mail.Ru Group is 20 years old !

As always, solve the quest puzzle here: puzzle.mail.ru .
UPD 10/22/2018 Medalists and Answers

Prizes are as follows:
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• The first who correctly solves all problems will get a set with Raspberry Pi 3.
  
• Another 20 prize winners will be selected randomly using random.org from those who solve all problems until midnight Sunday (October 21) Moscow time. The lucky ones will receive special prizes from DC, Disk-O, GeekBrains and other company products.

How to complete the quest

Login and password during registration are needed to continue the game on another computer. On what the quest began, on that and have to finish. And yes, you can only play on laptops and desktops, on smartphones and tablets will not work. This is not discrimination, you just need text and image editors.

The puzzle consists of 20 levels. At each level, it is necessary to find out (find or calculate) the secret word and enter it in the input field at the top.

Often there are clues at the level, but sometimes the opposite is superfluous distracting information. Tips are often hidden. Do not forget to look into the HTML-code of the page.

To solve the puzzles, you do not need to be able to program, the main thing is to have a basic knowledge of web technologies, computer science, know about ASCII, RGB and the number system.

Please note: this time the task can not take place in turn. When you are sure that you have answered all the questions, select “send answers” ​​in the navigation. If you want to participate in the prize draw, please leave a contact e-mail.

With all questions come in comments.

Please do not spoil the pleasure of others - do not publish the answers. On Monday, October 22, the right answers will be announced on Habré.

We accept congratulations on the anniversary!

UPD: The answer to the question is either directly “hidden” on the page or given the task of how to calculate it.
But it is definitely not necessary to guess what is depicted in the picture, or to select associations, therefore, for example, the answer to No. 2 is not a “ handle ” and not a “ bottle opener ”, and on No. 3 - not “ Lenin ” and not “ Ilyich ”, etc. P.!