Where do you guys practice CS Fundamentals MCQs and OA mocks?

I'm currently preparing for placements and want to improve my CS fundamentals, especially DBMS, OS, Computer Networks, OOPs, and SQL.

I’m looking for good resources/platforms where I can:

Practice CS fundamentals MCQs

Take timed quizzes/tests

Practice OA-style mock tests that include aptitude + CS fundamentals + coding

Get a feel for the difficulty and pattern of actual placement OAs

I’ve found a lot of random MCQ websites, but I’m not sure which ones are actually worth spending time on.

What resources/platforms do you guys use for this? Any recommendations would be really helpful.