Is it permissible to work for companies that analyze data for banks, insurance companies, and liquor stores to gain experience, given the need for work and the desire to return later to work in Islamic banks?

It is not permissible to work in data analysis for usurious banks or institutions that deal in unlawful matters; because the means share the rulings of their ends, and whatever aids in the unlawful is unlawful. This falls under cooperating in sin and transgression, which is forbidden by the Almighty's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and transgression." Neither a low university salary nor the acquisition of experience permits working in the unlawful. Rather, experience can be gained from institutions free from unlawful dealings, or in another place, or upon returning to one's home country.