Do you think it is possible to achieve a cool result without a fitness room? And working only on horizontal bars with additional weight? Your opinion?

It's not very clear what is meant by a cool result. There are usually three results: strength, muscle mass, endurance. Of course, you can partially replace the gym with bars and a horizontal bar if you use weights. Another thing is that in the gym it is much more convenient to do this, as a plus - you can train a much larger range of muscles, there is freedom of choice in alternating workouts. The same push-ups and pull-ups can be done on a gravitron (with reduced weight), which is impossible on clean bars or a horizontal bar.

Of course you can.

Exercises performed on the horizontal bar and parallel bars are basic. Pull-ups are generally the best exercises for working out the back, biceps, and forearms.

Many people think that the minus of the uneven bars is a concentrated work on the lower part of the chest, however, there is such an exercise as parallel push-ups, which, due to the greater range of motion, involve the chest as much as possible. Also on the uneven bars, the triceps and the front delta are perfectly worked out