mmm not really
no, it is totaly 100% free
No, Skype is free and calling other skype users is free. You can video chat, voice chat or text chat with them for no charge. However to call a landline or mobile phone, you must pay to use those...
Firefox is free.
Yes you do. You can pay via a credit card, or a gift card that you might be able to buy in some local hardware retailers or supermarkets.