first: may I delibarately destroy one of my figures/cities/buildings, for example to deny my opponent making use of my buildings, or (what's more important) to stop Russians from parasiting on my technologies? rulebook doesn't say a word, but I think it should be possible, say at the beginning of turn (when you place cities);

and second one: Russian ability states, that they may acquire technology known by opponent at no cost - but it refers to Research phase (normal R&D but for free) or it's additional tech gain?

a) No, you may not voluntarily destroy things.

b) In order to get the tech you have to move an army or scout into an enemy city, so this is done during your movement step. You can only do this once per turn.

Cities aren't conquered they are destroyed along with all thier buildings wonders and great people.

 I have an additional question about the Russians learning a tech through sacrifice. Can they only research a technology that legally fits on their tech pyramid or can they research any level tech?

I would say they must have a valid space on their pyramid, but then they do start out with a level 3 that is hovering at level 3 with no level 1 or 2 techs to support it. 

They have to have the legal space on the pyramid. Gunpowder and combustion could both destroy the buildings you seek to destroy. Unfortunately at a price, but it can get the deed done.

v3ct0r_m4yh3m said:

if i understand correctly you dont play it right. nothing hovers, everyone starts with techs at level 1.

Turric4n said:

p 11: under "Learn Starting Tech"

Note: The level of a player’s starting tech is irrelevant during
setup. The tech is always placed in the bottom row of the player’s
tech pyramid.

I still don't understand...So if you use your Russian army to gain one enemy tech in movement step, you can still research one tech in research step?

so you can gain two tech in one turn? am i right?

 yes. you have to get more techs per round in order to succeed with a tech victory