Your freckles and moles may darken more than the rest of your skin. You can apply sunless tanners to your armpits. Most people don't have tanned armpits, but avoiding the area with realistic results takes skill. Your belly button could darken too much. Rub it with a Q-tip dipped in lotion after you apply the sunless tanning lotion.
Scars are a bit unpredictable.
Mostly, they darken very little or not at all. If your sunless tanner does not contain sun screen and you will need sun protection, don't kid yourself. There aren't any sunless tanners which have adequate sun protection. Apply sunless tanners in the evening before you go to bed and use sun screen during the day. If you have a little bit left of different brands, you can mix them up in one container.