Even though they are grammatically correct, they don't sound natural. Here's my suggestion: I finally cleaned my room after a long time. Or I cleaned my room because I hadn't done so in a long time. I have done my homework because I am going to school tomorrow. Or I did my homework because I have to go to school tomorrow.

They are correct - you can reword it better though: I haven’t cleaned my room for a long time, so I cleaned it.

不对，

The grammar is correct but it sounds a bit off. For the first sentence I would rather say: • I cleaned my room because I haven't cleaned it for a long time. For the second one I would say: • I did my homework because I have to go to school tomorrow.