You can check prices on any Runescape website, but the gist of it is:
Coal 158gp-175gp
Cooked Lobster 274gp - 303gp
Raw Lobster 331gp - 366gp
Cooked Swordfish 418gp - 462gp
Raw Swordfish 472gp - 521gp
Willow Logs 18gp - 19gp
Green Dragonhide 1,562gp - 1,727gp
Dragon Bones 1,775gp - 1,962gp
theres great guides on how to bot now there is a new program called rsbot you can find guides in the cheating section also the grand exchange is basscily like selling to a general store because it sells right away but its to players for a better price also there is some great f2p mining scripts
all of the above mentioned is f2p except Dragon bones and dhides, but the quickest way would definitely be to fish or mine, fishing is good bc you can raise your cooking too or just sell them raw(worth more)
Yes, they all can, Scar is more complicated than rsbot, if I were you I would use rsbot, it is safe and there's tons of scripts, it's easy to download and get working. Your other option would be to just do it yourself.