you can start using anti-aging cream and other stuff at any age but its best to start when your young because its like a prevention for the future.

Anti-aging creams are usually used by people after attaining the age of 30. But there are some cases where wrinkles start appearing at an early age and then these creams could be used. Some good eye and face creams can be found at zenmed which is a world class skin care product company and has been around for over a decade. Most of the products are natural and can be used on any type of skin.

sunscrean is ok but anti aging should be used after35
Avoid it you can try home remedies
carrot mahed -1
Lime juice-1tsp
almond oil 1tsp
Mix all ingredients and apply on the area where wrinckles are likely to appear

Start from where you are! 20 is just good, use before you look at the wrinkles! you know what I mean?

For which type?: get with local stores or your doc for the perffect effect

30+

or when you start seeing the first signs of wrinkles i guess.

you are 21. you should not worry about that. just continue taking care of your skin by cleaning it, avoiding foundation that clogs your pores, and using your sunscreen. enjoy your youthful skin good luck!