I have stolen tech in GC2. In one game after maxing out the espionage I started getting a tech every 10-15 turns. In other games none.

I don't know if it is just random or what determines your success but it has always been later in the game, well after you have maxed out the spying.

Yeah it's possible. You can also learn/steal new techs when you conquer enemy planets!

Yesterday I read the whole manual. And I think it mentioned something about the ability to steal techs through espionage. So I think it's possible

Once you get high up on espionage (there are several levels, but I dont know exactly what level you need to be in order to start stealing techs) you can steal techs. In a recent game where I was pumping the max amount of money into a player for espionage (well over 200bc per turn), who were also fairly ahead of me in tech, I was getting probably 1 tech every 10-25 turns. Maybe I was getting lucky? Maybe not. I dont know.... I generally find espionage to be a waste of valuable money in its current form, unless under certain circumstances. But, anyway, it is possible to steal techs (through espionage and/or planet conquering) that you do not have the pre-requisite researched. ie, you could have Sensors Mk2 researched, and steal Sensors Mk4. You still have to research Sensors Mk3 in order to advance further down that line, however. Hope this helps.

after you have reached the max level of intelligence about a race and suddenly u decide to not spend money in inteliigence yuor rank of intelligence will drop or remain the same for the rest of turns?why you say that intelligence is a waste of money? doesn't it give u vital information about enemy ships or other important aspects of the game?

Well, I would agree that 200 per turn is excessive but as little as 15-20 per turn will slowly but surely get the info you want.. I think espionage is valuable to get fleet sizes etc.

The thing that annoys me is clicking a minor race starbase and being told that I need to spend more money on espionage when that is not possible. If I can't spy on them at any cost, they shouldn't have secrets.

Another thing that was in the beta and may or may not still be, is a random event is where you are told that such and such minor race has stolen the entire research of one of the majors and is willing to trade it for a planet. When you click okay on the splash screen that is the last you ever hear of it. If you speak to the minor race involved there is no such research available for trade.