[AmgedIsmail]

Hello,
What is the difference between these two clause particles?
I studied some examples for both and I didn't see any difference.
Here I will give you an example.

Although it's cold, I went out.
samui desu ga dekakemashita
さむいですがでかけました。

Can I use keredo instead of ga?
samui desu keredo dekakemashita
さむいですけれどでかけました。

Another example, that both mean "and"

I read the book, and it was interesting.
sono hon o yomimashita ga omoshirokatta desu.
そのほんをよみましたがおもしろかったです。

Can I also use keredo here?
sono hon o yomimashita keredo omoshirokatta desu.
そのほんをよみましたけれどおもしろかったです。