You're a bit confused))

For outside, there are 2 types of filter, media and cartridge. All that you need outdoor is quality sediment filter. Cartridge filter can be as low as 1 micron, realistically 5 is good enough, 20 can work too if your water is very dirty. Media filter in theory can be 20 micron, reality it is 40 micron and it requires backwashing.

I think I posted it somewhere in this thread, but can't find it. In my opinion, it makes 0 reason to go for media filter. No matter how many layers you have, no PoE filter can give you drinking water, it's pre-filtration at best. Media filter only makes sense when you have a known, specific problem with your water you want to address, say your water has extremely high sulfate content, then you may need to have sulfate media filter.

Can you filter with carbon block outside? Yes, why not. But it is not necessary. Also, you will need to make sure your water tank is in good condition, since if no chlorine enters it, there could be alien life appearing (algae etc). Your pressure will drop, etc.
By the way!
After monitoring Lazada, local websites etc, I want to say to everyone do not trust description you see on Lazada/Lelong/Shopee or other local online shops.

Most people will copy information from each other and there is so much false information floating around. If you check Lazada, 3M AP902 somehow has carbon in it (FALSE), made in USA (FALSE). Aquasana is marketed as made in USA (FALSE again). I do not know if these are lies told to sell systems or just because sellers are ignorant and they assume if it's US company, then it is made in USA. AP902 is even shown to remove chlorine, heavy metals and bacteria BY VIRTUALLY EVERY SELLER, when all it is a sediment filter....

I wish I had more time to debunk those myths. Hope 1 day I will start doing it with my website/video blog. I don't mean all products are bad, not at all, just don't say that the filter can do what even manufacturer says it cannot do, cmon! (sorry, a bit frustrated with all these "little inaccurate listings" as one seller on Lazada replied to me when I challenged him).

Indoor can be any price, but it depends what you want it to filter. What is your goal? Pure and safe drinking water or just get rid of sand and chlorine smell and then boil that water?

maybe around 600-800 range, you can do it with 3m and aquaphor. if there is a will there is a way 

aeiou228 correct or not?