am i allowed to...

hello to all of you... i have started blogging recently and i dont have much knowledge about monetizing my blogs.started off with google adsense.i was wondering if i could place other ads also with google ads.

and i came to know about getting paid to write posts on my blog like pay per post.can i register the same blog in various programs of similar kind or i have to make separate blog for every other program which pays to post or to review certain products and services.suppose if i have a blog about mobile phones and i want to use it to get paid by writing about mobile phones,do i have make separate blogs for every program or i can use the same blog for various programs.