Can melasma, blemishes, and skin whitening be treated with cosmetics?

Basically, I'm curious if treatment is possible and if anyone has seen results.

I didn't used to have many blemishes, but perhaps due to my age, I am getting a lot of unidentifiable ones.

I wonder if I should use whitening creams or blemish products in advance, even as a preventative measure.

I wasn't sure if applying sunscreen frequently was the only way to survive.

Even if what has already happened cannot be helped

Should I apply something to prevent it from happening in the future?