2) By test scripts can you clarify that you mean VB code scripts created in the Excel Visual Basic Editor? If so, and you want to execute these from QC I would think you would need to load them all into QTP and save them from there.
While I have been working for Businesses that are Vendor partners with HP, IBM and Microsoft, my opinions and advice is my own.
The solutions provided are either sourced from my own scripting libraries or from a quick Google Search.
How many testcases are you looking to modify? Reason why I ask is that there's a way to do this but requires some setup and modifications of the TC in question via the DB. If the number is around 100 or lower it would make more sense to perform it manually (TC by TC).
Number of tests to mofify is above 1000, i have been told that we can download the testcases from QC to excel using APIs, adding a column of "Type" as "VAPI-XP" and then upload it back to QC.
But, I wish to know how to upload the QC test scripts to Quality centre.
That is, i have the scripts (written in Java script) in a local desktop and it needs to be uploaded to QC (Test script tab) for a particular testcase.