Firstly, welcome to the forum, and well done on cracking the clues
Unfortunately due to the information your asking for your very unlikely to get the answers you expect or want.
1. Yes, there is a way to know accurately... you open it up
On the basis your not at that stage yet, if you've solved the clues that should give you a good idea
2. Again, that's not the kind of question thats gonna get an answer to outside the 5% club, and again if you've solved the clues they should help.
3. This kinda relates to the previous question. In general though if you have an idea then give it a go, if it's not working then try something else.
The thing to remember is that all you need are the 10 clues that came with the Isis and the 11th clue which is scattered all over this forum.
Read the forum if you get really stuck, there's
loads of information here
Good luck
Chris