What is the reason for worshipping Allah; is it for His pleasure, or to enter Paradise and be saved from His punishment, and who are the Ahl as-Sunnah wal-Jama'ah currently?

The purpose of creating jinn and humans is to worship Allah the Almighty alone. Whoever worships Him as He intended has fulfilled the purpose and attained His pleasure and the happiness of both abodes.

Ahl al-Sunnah wal-Jama’ah are those who adhere to the Book of Allah and the Sunnah of His Messenger, peace be upon him, according to the understanding of the Salaf of the Ummah. They are not confined to a specific group. So, whoever possesses these characteristics is one of them. A person’s closeness to or distance from them is determined by their closeness to or distance from their methodology.