AdSense rules cannot be thought of in really concrete terms. They are purposefully written in vague weaselly language and they are interpreted differently depending upon who you are.
The official rules are written in two documents:
However, there are other rules which are enforced from time to time by the AdSense Abuse staff which are not published publicly. In addition, the published rules change from time to time.
Any advice you receive here could very well be considered wrong by Google. Heck, it could be considered right today, but wrong tomorrow. It could be considered right by one person at Google, but wrong by another person. Google rule interpretation is both arbitrary and capricious.
If Google "feels" that you are an "ok joe", one set of rules will be applied to you. If Google "feels" that you are a "nogoodnik", you will be judged by a different set of rules.
All that being said, I'll try to make some guesses regarding the items you listed.

Originally Posted by
Szise
- Is against Adsense rules to force indirectly the users to click your ads by hiding the url form making them search for it when your page is full of ads.
This violates the "spirit" of the AdSense rules, if not the letter. I would not try this, but many people do it and get away with it.
The relevant section of the AdSense Program Policies is:
In order to ensure a good experience for users and advertisers, publishers participating in the AdSense program may not ... Format site content so that it is difficult to distinguish it from ads.

Originally Posted by
Szise
- Is against the Adsense TOS to place ads very close to the url form (must have a space between url form and ad unit.
This violates the "spirit" of the AdSense rules, if not the letter. I would not try this, but many people do it and get away with it.
The relevant section of the AdSense Program Policies is:
In order to ensure a good experience for users and advertisers, publishers participating in the AdSense program may not ... Format ads so that they become indistinguishable from other content on that page.

Originally Posted by
Szise
- Is against the Adsense TOS to place ads on proxified pages.
This is not mentioned in the AdSense Program Policies, but if you think about it you'll see the problem. If you put AdSense on proxified pages, you are putting your AdSense ads on pages which you do not control. Therefore, any violations of the AdSense ToS or Program Policies on those pages may affect your AdSense account.
One risky trick which you could try would be to replace other people's AdSense blocks with your own, under the theory that "if they are already running AdSense, they are probably already compliant with the AdSense rules."
I can't say that I'd recommend this, unless you don't mind losing your AdSense account -- but I also don't see where it is specifically not allowed.

Originally Posted by
Szise
- Is against adsense TOS to make a site about cars, write about cars and advertise it as proxy.
This violates the "spirit" of the AdSense rules, if not the letter. I would not try this, but many people do it and get away with it.
The relevant sections of the AdSense Program Policies are:
Do not place excessive, repetitive or irrelevant keywords in the content or code of webpages.
... and ...
Create a useful, information-rich site and write pages that clearly and accurately describe your content.
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