Permissible and impermissible items of trade

Q: Am I allowed to sell a book I got for free?

I ordered a secondhand book online for a class I'm taking. It arrived very quick, and it looked completely new, not secondhand at all, but I no longer needed it as I had already bought the ebook. I put the book for sale online. What I usually do is sell it for 2x or 3x the price I paid, but still cheaper than the retail price. But then, a few days later, I got another copy of the book in the mail, and this one looked more like a secondhand book with highlights and stuff. I thought maybe the company made a mistake and sent me 2 copies, but I just remembered, about a month ago, I had filled out a form on the book company website pretending to be a teacher to see if I could get the book for free. I have done these before, and they never work, so I was just doing it for fun. My answers were absurd, with a fake name, institution, etc, and I thought it would eventually take me to a page with more security where I would have to provide proof of identification, but the form suddenly ended and it was submitted. I had completely forgotten about it, and there were no updates in my email about the book, whether my request was approved or whether the book was shipped. I still have a feeling that this company is likely the one who sent me the book. So, my question is, what do I do with the book? I didn't mean to get it like that, like I didn't think the form would work, but now that I have it, is it permissible to sell it?

Q: I read in Behashti Zewar that it is not permissible for women to wear artificial rings.

1. Since I was unaware of this ruling, I already have many such rings that I used to wear. What should be done with those rings?

2. I have given rings as gifts to many women in the past and my jewellery business gave me profit from selling artificial rings. Will I be sinful for this? What should I do now?

Q: We have recently received stock of an Islamic toy which we were unaware had music... The toy has many beneficial learning pages such as duas, surahs, Arabic alphabets, etc. but there is a button which plays nasheeds with musical instruments in the background.

Will it be permissible to sell such a toy? If the toy is sold with a note on how to remove the music and if the customer purchases it and chooses not to remove the music wire, will the seller be sinful?

Q: Whats the ruling about Bitcoin? Is it halaal or haraam?