any upgrade recommendation from SCA vision to 21.1? also any documentation? Can I reuse the same code in SCA 2021.1?

Short answer: no. in 2021.1 you should create extensions which did not exist in SCA vinson. Many files have changed as well since that version and in the source code typescript is being used. There are many things to consider.

You will need your SuiteCommerce developer (if that is not you) to make the extensions using extensibility api. This is good because it makes it easier to update to the latest version