Q1. My doubt is that whether the dynamic overclocking occurs for all cores together or each core is dynamically overclocked at different frequencies as needed.
According to my monitoring program, the cores in my CPU have independant clock frequencies of eachother. This is probably intel speed-step working [Citation needed], (since naturally you cannot set individual clocks for your cores). The cores throttle based on system load, as clearly seen in the first screenshot:
As you'll notice, CPU #2 is at 9% load, and because hyper-threading is enabled, it corresponds to Core #1 which is at a much higher frequency than all the other cores.
Here is another interesting screenshot where 3/4 cores are at different frequencies, but the CPU load does not really match that perfect.
Both our CPUs have Idle States, Intel® Turbo Boost Technology, and Enhanced Intel SpeedStep® Technology. So unless the only reason why my cores have independant frequencies is because it's newer, your CPU should be working the same way mine is.
Q2. Does the increase in clock frequency above the base clock is the only way this gadget shows the turbo boost? If yes then again they are showing the single textual increase in frequency value as turbo boost.
Turbo boost is when your cpu core(s) throttle over the base frequency. My CPU has a base frequency of 4GHZ. However, if I put random loads on my cpu..
The frequency will sometimes get boosted to 4.2GHZ maximum. It appears that it will only turbo boost the cores when the load is not that large. Here is a screenshot when I'm stress testing the cores:
So @Darth Android's comment is accurate about this behaviour, how it will only turbo boost when part of the processor is idle.
Q3. Is there any better tool.
You can find the tools I used on http://www.cpuid.com/
CPUID brings you system & hardware benchmark, monitoring, reporting quality softwares for your Windows & Android devices