I have created SDF project through VS code, Now I would like to make that project available "public", What is the process? as I am still confuse between SuiteBundler and SDF and SuiteApp

First you have to talk to a rep and get a SuiteApp ID and then build your suiteapp w/ your components having the SuiteApp ID and then you have to go through the BFN certification and then you can get on the store.

But, I just want to test my SuiteApp, just like SuiteBundler 'Shared' bundle, Do NetSuite support that feature?

You can just install yourself via vscode into the account you want to test in.

If you already have a Publisher ID then you can deploy a SuiteApp using the IDE/CLI before it's gone through the BFN process. This is not "public" until (as creece said) you get it through the BFN with NetSuite and put it into the marketplace.

This helps me a lot, Thank you all.