I have a question. Is a certain xbox live for free (1) ,like for gamer points and unlocking achievements (2) ?
The question is a bit vague but let me try:
(1) Yes. If you sign up for a
silver account, it is free. The silver account will allow you to do everything on xbox live like voice chat and downloads, but you will not be able to play games online.
To play games online you will need to sign up for a gold account, which you will get charged for on a monthly, 3 monthly or yearly basis, depending on the package you choose. Remember that you'll need internet access regardless.
(2) Adding gamerpoints and unlocking achievements is in no way related to the xbox live service. You will still unlock achievements and add points to your gamerscore, regardless if you are an xbox live subscriber or not. But, relating to this, is your gamertag. Now, it is important to check the web for gamertags in use (there are a number of sites with lists) and pick one that is not in use, or that you know will not be used by anyone on the xbox live service. Reason for this is that your gamerpoints, saves and achievements are linked to your gamertag. If you eventually activate the xbox live service, it will check if your gamertag is in use by someone else on the network already. If it is, you've got a problem. You will have to change your gamertag to something new, and in the process you will lose all your current game progress.
Remember, gamertags cannot be changed before it is registered on xbox live. Even when registered, they can be changed but that is charged for.
Hope that helps.