I need some info about account collection:
1- Is 10 the minimum level of a char to not have the account deleted if not used?
2- Does high craft level prevent your account from not-use deletion?
3- Can I delete an account made because of a mistake? (or because my char sucks )

There was no accountdeletion,only a inactive chardeletion

1-Last Char-Deletion(first one i ever saw) was pronounced before by the UthStaff.
2-They said also conditions for chardeletion(I think last one were chars between lvl 1-10 or sth like that which are a longer time inactive;means they deleted these x beginner-guild chars)
3-You can delete all your Chars to get your Account free, but at every char you must accept deletion...so it shouldnt be normal that you delete a whole account with 3+ Chars

3- I meant if there were a command to completely delete an account.
Example:
I insert the wrong nickname and create another account, I want to close it^
2- If in an account there are lv 1-5 characters with high level craft skills will they be deleted if not used?

there is something like 1-5= 1 month
5-10 = 3 months

i am not sure about the values... but if you wanna keep a char as mule or anything else, just make it crafter. Crafters account are not erased

3- No, you can't do that by yourself. However, if you delete all characters from an account it will be purged from the DB during the next clean-up action.

And if I have an account with low level but high craft skill characters? Will it be deleted after some months?

During our last big DB clean-up (cf. http://uthgard.the-bart.org/modules.php?name=Forums&file=viewtopic&t=3500) even a single point in any crafting skill would have been enough to save that character/account. If we decide on a different procedure you'll see some information in the forum prior to the deletion.