At what level are there drug tests, anti cheat measures, and segregation in tournaments?

I'm wondering if weak GMs play in regular tournaments or GM only tournaments. 

...and shoe inspections!

The only substances they're going to find are allergy pills and vitamins

What is the attitude of actual high level chess players to caffeine?

Nicotine?

Have any grandmasters been caught with amphetamines, and if yes then apart from legal punishment were there any effects to game scores?

You probably don't have to worry about it until you actually become a GM, which may not even happen.

Just the two options?

There must be tournaments where grandmasters, especially weak grandmasters, play non-grandmasters, because people somehow become grandmasters. See the title requirements:

https://www.fide.com/fide/handbook.html?id=198&view=article

Note:

If grandmasters were to play each other only and refuse to play chess with people who are not grandmasters, no one could ever meet a grandmaster norm and therefore no one could ever become a grandmaster. If a bunch of international masters play each other, but don't have enough opportunities to meet grandmasters - foreign grandmasters at that, see

then no matter how overwhelmingly some of them dominate over the others and how much Elo they reach, they never qualify as grandmasters. A position of some Soviet chess players, I believe.

But what is the interest of grandmasters in playing non-grandmasters and thereby giving away grandmaster norms?

Of the weak grandmasters... Bisguier is dead, but Nikola Spiridonov lives - and plays. Age 81, Elo 2150. (A genuine grandmaster - peak rating 2490, back in 1976 when he was 38).

Who get to play Nikola?

This should be locked!