Hard Disk Management Logical Partition Extended & Primary Partition

In the Linux partition /dev/sda4 is always consider as the extended partition.
Primary partition is used for maintain the operating system.
In the hard disk it has four primary partition,
while booting Only one primary partition is active and renaming partition it will ignore.
1)One of the Four primary partition can be assigned as extended partition.
So In the hard disk we have only one Extended Partition.
2)that extended partition can be divided into multiple logical volume,
3)Logical volume it can not be Primary Partition,
4)If we want to increase the partition
4.1) we can not increase the Primary partition
4.2) we need to increase the Logical partition from the extended, Here we can exteded upto 64 Logical volume,