It seems you are trying to install the version 9.5.1 on an unsupported Operating System.
Please review the KB : https://kb.informatica.com/solution/23/Pages/61/509827.aspx
For 9.5.1 HF1, if you want to run the installation on Windows only Windows 2008 and Windows 2008 R2 are supported.
Isn't there any workaround because finally I have to upgrade Informatica to 10.2 and once I downgrade to 2008 just for installing 9.5.1, I still have to upgrade it to 2012 R2 for Informatica 10.2.
Can I do it in an extra machine with 2008 installed and install Informatica 9.5.1 there connecting to same Database repository and after upgrading repositories then Installing 9.6.1 in previous 2012 R2.
First it's ugly that you posted the same question twice, this forces people like me to respond to two posts with the same responses. No fun for me.
Second no, there's no simple "workaround". You have to follow the PAMs (Product Availability Matrices) as stated by Informatica. There's no other way. I've seen hundreds of people over the past 18 years trying to take such "shortcuts", and none of them worked reliably. Don't waste your time by trying such "workarounds", they simply are not supported and (in particular under Windows) most often lead to all sorts of severe trouble. Nothing but a waste of time in my experience.
And yes, that DOES mean that you need several Windows installations to perform those intermediate upgrades in a safe manner. Again, I've never seen anyone succeed in finding "shortcuts" which work reliably.