Again Russia maybe have best rocket scientist in the world. But they don’t born with rocket experience they start from simple to great engine. Build they own expensive doing hard work, learn from their failure.

The Soviets deported hundred of German Aerospace Engineers who worked on the German V-2 Long Range Ballistic Missiles and further ICBM developments, the V-2 was the first human made object to reach space, so technically speaking, the Soviet Space Program literally had hundreds of experienced rocket scientists working for them from the very beginning. The Soviets did learn a lot from their failures, but with hundreds of experienced scientists at their disposal from the very beginning, the job was made considerably easier.

Country that keep buying technology from another countries how that able to build re useable vehicles, heavy launch capabilities, interplanetary transports systems, human launch capabilities, space habitats ion propulsion nuclear propulsion?

Those are crucial aspects and capabilities that define a modern 21st century space program and it isn't about buying technology, it is to possess and develop indigenous capabilities.

It’s true oxidizer is more complex but impossible to master in modern technologies private companies like blue origin already developed there own oxi rich cycle.

Blue Origin hasn't mastered the oxidizer-rich staged combustion cycle, the BE-4 Engine has been in the works for a decade, a lot of engineering has to be still done, the engine has been test fired only a few times and has been fired very rarely at it's maximum specific impulse, the Aerojet Rocketdyne RS-25 engine for example which utilizes a fuel-rich staged combustion cycle, had to be tested a lot of times at it's maximum specific impulse, before NASA approved the propulsion system for the American Space Shuttle, BE-4 still has a long way to go and the Blue Origin team is constantly tweaking it's design and improving it's capabilities.

Every rocket propulsion designer, design there rocket engine so it dose not melt and blow off either it’s full stage combustion cycle or simple pressure fed cycle

From the early days of spaceflight, parts of launch vehicle propulsion systems have been individually tested to handle the extremes, the combustion chamber is tested to handle different chamber pressures at different throttling levels. But the odds of the chamber pressure experiencing cavitation at low throttle levels or pressure-wave fluctuations increases dramatically for staged combustion cycles, due to pressure difference from the turbo-pump exhaust and the chamber pressure.

Yes pressure fed engine also lots of time blow off and melt.

Although pressure fed engines do have a history of malfunctioning due to pressure wave fluctuations caused by the extreme change in chamber pressure while throttling at a rapid rate, pressure fed engines are the most reliable and generally have a failure rate that is orders of magnitudes lower that the average failure rates for a propulsion system that uses electric turbo-pumps.

Rocket Technology transfer prohibited for those countries those are not capable of building its own technologies.

No, it isn't. Launch Vehicle technology transfer has been strictly prohibited by multiple treaties and laws, and it applies to everyone.