yes, you need to cancel (especially if you dont have any plans to go back BUT if you didnt, your RP will automatically expire upon 6 months of non-entry to Qatar.)
however, if your current sponsor is kind enough to provide you NOC, you needn't need to cancel. you can transfer your sponsorship directly from one company to another.
yes you need an exit permit.
yes, you need to cancel (especially if you dont have any plans to go back BUT if you didnt, your RP will automatically expire upon 6 months of non-entry to Qatar.)
however, if your current sponsor is kind enough to provide you NOC, you needn't need to cancel. you can transfer your sponsorship directly from one company to another.