Also, is it 6% a year or 6% per time you get interest?
Annual rate
Yes the amount of cloak you receive is 6% of mature coin wallet balance per year.
Your network weight determines the amount of time required to receive reward.
Your network weight is the percentage of total cloak in existence you own.
You don't need to mint all the time, just the time that is specified by "time to earn reward".
If you have a very large balance it may only be hours, very small balance could be a month.
You can mint as often as you want to earn a reward but it will always be 6% a year.