A little quote It's frin ADsense TOS. Also if you try to put more than 3 content units on the same page ... not all units will be displayed. BUT there are several sites in internet, that displays more than 3 content units on the same page. Here is a screensot of the page on which i calcualate 7 AdSense content units (regarding source: 3 of them use google code + 4 links with iframe links from doubleclick.net). As it's very popular medical site i save this screenshot with low resolution. Correct me if i'm wrong. Is it TOS violation?
If the ad code is put into a different php page, and the index page includes the other php page with the ad code on it - Google classes this as multiple pages. So yeah, you can have more than 3 ads on your site. Google doesn't really care tbh, as long as they are getting legit clicks.
Of course google limit ads on the same page. You can try yourself (even if the page is very-very large page )
I don't think so ... even if you include/require or embed differend php pages -google or users check it as one page. Another thing is <iframe> pages (as in the situation above)
3 Ads per page and a Google search bar. If they have more and Google are not worried then they most likely have a premium account.
Actually it's 3 ad units, 3 link units, and 2 search bars...enough to make the most spammy looking site anyone could ever dream of.