No sorry, that didn't solve. But following worked:
After importing mybb, upgrade it to v1.16.0 which produces "Error: ENOENT: no such file or directory, open '/nodebb/node_modules/nodebb-plugin-require/plugin.json' " as mentioned above.
Back up both database and any image files imported from mybb under public/uploads/files
Delete whole nodebb files and database
Install original v1.16.0 (git clone -b v1.16.x https://github.com/NodeBB/NodeBB.git
Remove only the database, then restore database and image files using backups
Works well, it doesn't produce any error even after installing quickstart plugin.
Additionally, https://github.com/NodeBB/nodebb-plugin-quickstart doesn't work on v1.16.0.
It shows following error on Chrome and the page got frozen while loading:
colorpicker.js:11 Uncaught TypeError: n.ColorPicker is not a function
at HTMLInputElement.<anonymous> (colorpicker.js:11)
at Function.each (jquery.js:381)
at C.fn.init.each (jquery.js:203)
at Object.n.enable (colorpicker.js:8)
at o (admin.js:31)
at Object.i.init (admin.js:9)
at Object.execCb (require.js:1696)
at n.check (require.js:883)
at n.<anonymous> (require.js:1139)
Anyways, it's not to be discussed here I guess.
Thank you very much!