A journal has accepted my paper which has multiple indexing including google scholar and is open access. But it ain't scopus indexed. Does that make the journal less desirable or credible?
This depends on the requirements of your institution and country. For example, in my affiliation, the papers that have the greatest "value" are those indexed in JCR, Scopus or CONACyT.
You could consult with some researchers in your institution and see if there is a national system of researchers in your country with key indicators. In my country (Mexico) there is the SNI (https://conacyt.mx/sistema-nacional-de-investigadores/).
No. It doesn't, those credentials and indexations usually take a lot of time and money. You should keep publishing because it's good practice, and top journals are quite difficult.
Google scholar is (just) a search engine dedicated to scholarly/academic article, however, it is not an indexing criteria/authority. It can index any journal type regardless if the articles are peer-reviewed or quality of article or journal as a whole.