Hi @Nandujee,
Please find below answers to you questions:
1. What is the use of this project "spa-project-core"? I understand the SPA page is created using this SPA template.
In general this is some sort of foundation for your SPA project. It mainly provides support for hierarchical model of sub-pages. You can find more info under https://github.com/adobe/aem-spa-project-core
2. Shall I copy this project "spa-project-core" inside my project and customize it to my need, is it advised?
No, coping aem-spa-project-core into your code is not the right way. You should add it as a maven dependency - see installation section https://github.com/adobe/aem-spa-project-core#installation
3. As per my understanding, libs folder components would be updated on AEM upgrade or SP installation. When would this project "spa-project-core" upgrade?
aem-spa-project-core have it's own lifecycle that is not directly connected to AEM or SP release cycle. You should track new version releases by yourself, and decide if new version is providing features or bugfixes that are critical from your perspective. Of course sometimes after SP upgrade aem-spa-project-core could be required anyway.
There is a direct dependency between aem-spa-project-core and core components, so you should be aware about that, and when you decide to upgrade core components version verify if aem-spa-project-core needs update as well.
Assuming you would like to use Angular, below resources could be interesting as well:
