Those 2 wheels work like a perfect sundial.
No they don't. They're flat. The timespan from one hour to the next on a flat sundial varies from season to season. At the same time that that temple was being constructed, people elsewhere had developed curved sundials that overcame that key problem with flat sundials.
How were ancient Indians able to perform such mind boggling calculations whithout any kind of technology, is there any other way to make such huge sundial without modern technology?
What mind boggling calculations?
If one defines time as that quantity which is measured by those sundials, then yes, they accurately measure time to the minute. But that's just a tautological definition. That isn't how we define time anymore. There's a point in the video where someone points to his wristwatch, implying accuracy to the minute. This is a blatant falsehood. There are two key issues with this, the equation of time and timezones.
The equation of time represents the difference between apparent solar time (time measured by a perfect sundial; keep in mind that a flat sundial cannot be a perfect sundial) and mean solar time. Mechanical, electronic, and atomic clocks are designed to measure mean solar time. Apparent solar time can differ from mean solar time by up to 16 minutes. The equation of time was known to ancient Greeks, and possibly ancient Babylonians before them.
For a long time, local apparent solar time was deemed to be the true measure of local time, while time on a mechanical clock was deemed to deviate from this. This point of view switched with the development of increasingly more accurate mechanical timekeeping devices, coupled with the inability to tell time by a sundial at night or when the sky was overcast. Now we tell time by our mechanical or electronic devices, preferably synchronized with atomic clocks.
The other problem with that part of the video is timezones. India has one timezone. If someone in the far eastern part of India called someone in the far western part of India and compared the time on their perfect sundials, they would agree to disagree by ninety minutes. They would however agree on the time displayed on their cellphones, and that time would disagree with the time displayed on their perfect sundials.