Question Is there any free version (can b used even after 30 days free trial) of Aida64 for cpu tress testing for overclocking purpose?

There are a bunch of tools. Aida64 is just a packaged solution with lots of fancy features so you have to pay for it.

hwinfo64 will give you pretty much the same sensor data.

There are a number of different free stress testing/benchmark software. People tend to use cinebench because it pounds a cpu and is a free tool.

So if you are willing to build your own you can do it for free. You must pay aida64 employees who make fancy stuff like being able to monitor your pc on your phone.