A 'premium rate' number - is one that's charged at a (often much) higher rate than normal. A 'normal' number in the UK is only charged at a few pence per minute - premuim rate n umbers can cost 150 pence per minute or more ! A proportion of the cost of the higher charge goes to the service provider (in addition to BT taking their 'cut').
Premium-rate numbers in most countries are intended for domestic use only. It is very difficult and complicated to work out the billing details to permit international calls to national premium numbers.
0800 numbers are used for making and receiving free calls. Also the 0800 numbers are used for toll-free calls This is usually international.
In general, calls to toll-free numbers from mobile phones will connect, and you will not pay any long-distance charges, but you will usually still pay the airtime charges.
Unless it calls for premium gas in your owners manual your wasting your money using premium.
slander
Yes, but only if you download the premium...
A toll-free number has no long distance charge associated, but calls from a mobile phone (cell phone) will still incur airtime charges, the same as local calls.
If you make a lot of international phone calls for work, whether you work from home or at an office, you should look into ways to make cheap international calls. Your regular phone provider probably charges exorbitant fees for international calls, but many companies allow you to make international calls very inexpensively if you purchase their international plan.
If you mean a UK 090 premium rate number, then it is normally not possible. You may find a prepaid calling card that offers access to these numbers, but generally telephone companies will not connect premium rate calls between different countries due to the difficulties of billing and legal issues.
The additional cable is for making phone calls
It does not, in all countries. Different starting numbers are used for different purposes - premium rate calls, non-geographic or local, toll free/freephone, etc.
No, it is illegal. The only calls that you will be charged for answering (other than airtime charges on a mobile) are "collect" or "reverse charges" calls where you explicitly agree to pay.