Those are loyalty customer that already spent 2 Years with TM.
That is the return for their support on TM.
Yes, unlimited.

Difference, you can check at 1st Post of the thread.

Main difference is Upload Speed, Ping, Stability & Technology are totally different.

Example: You can drive a car at 8Mbps to KL but went return you can only drive at 512Kbps.

Copper Line will degrade day by day, Fibre Line will not easily degrade.