Flight depart delayed by almost an hour but arrive almost on time? [closed]

Welcome. It may not be obvious to newcomers, but this site really encourages asking one single question per post. If you have multiple questions, post them separately. In my answer below, I'll address what I understood to be your main question; am I entitled to any compensation

The airline got you to your final destination on time. That is really the only thing that matters in terms of compensation. Whether or not individual flights in your itinerary were delayed is irrelevant.

Nothing you describe is in any way unusual. Airlines build a little margin into their schedules so that minor delays wont have too serious effects. Also, having to wait, on the ground, while the aircraft waits for its takeoff slot is also 100% normal. Unless it leads to a significant delay in arrival at your final destination, it isn't cause for any compensation.

For my first flight, I almost couldn't catch up the other flight due to delays, what compensation I could get?

None. It's inconvenient to find that you have to rush across the airport to make a connection, but ultimately when you say you "almost couldn't catch" the flight what you mean is that you had to hurry but you did catch the flight. You aren't eligible for any compensation.

What compensation I can get for flight delayed while we are inside?

None. If they get you there on time, you don't get compensation for being bored before take off.

In Doha, how is it possible to have 20 flights departing in 10 minutes interval?

Doha is a large international airport with multiple runways. A flight every 30 seconds isn't particularly remarkable.

Do flight company allowed to have us waiting in flight and do nothing?

What would you rather they do? Your delays were long enough to be irritating but not all that long (both under an hour). It's time that you would have been sat on the plane anyway. De-boarding and re-boarding would probably have only delayed the flight even more.

How is it possible that flight 2 could arrive almost on time with an hour delayed in departure?

Schedules typically have some buffer built into them, and planes can fly at a range of speeds. Maximum cruising speeds are typically not used, because fuel efficiency is better when flying a bit slower. If a flight is delayed, it's common for the plane to fly a bit faster than usual (sacrificing fuel efficiency for less disruption to the schedule). Doha to Kuala Lumpur is a pretty long flight, so it's not surprising that they made up for most of the delay.

The middle east hubs works in such manner: airplanes should land near at the same time, and depart at the same time. So you have all connecting flight ready (in one direction), so the airplane are on air most of the time, so cheap. On other hubs this is less evident: arrival on intercontinental flight are often not too late, so that there are connecting flight. Departure of intercontinental flights are choose after most local connecting flight arrived (but because of business travel, morning and evening flight are already frequent, so you do no notice much). Note: this is just from/to the main hub.

Compensation is about arriving late. And in any case 1 hour is not enough for any type of travel. Departing one hour late do not requires (in my opinion) special assistance from airline. For sure no compensation. [Early departures are different].

Flight length depends on many factors, mainly bad weather/head winds. So what you see in timetable is mostly on longer side (also to reduce compensations). It is frequent to arrive earlier.