"Is there ports binding function to instead of MLPPP?"
Sometimes there is, but I believe it would require extra (often external) hardware. (E.g. T1s using ATM and IMA).
"Something like port-channel."
MLPP is something like port-channel, but also a bit different. Both, though, bind together multiple physical ports into one logical port.
"I am a little confused about that T1 controller setting "group-channel", is that a kind of port-channel?"
When using a T1 (or E1, too, I recall), you can divvy up its bandwidth into channels, or not. The former allows you use one or more 64Kbps (adjacent) channels to form a subinterface. So, using channels, is somewhat, too, like a port-channel and/or MLPPP.
If you did have subinterfaces, it might be possible to bind them into a MLPPP interface too.
I recall (?) with a single T1 channels you could do things like have four routers, each with a T1 connection. HQ router takes its 64 channels and might use 32 of them to one of the other routers, and 16 channels to the two other routers. Since those other three routers are not using all their 64 channels, you also have the option to use the channels for connections between those routers too.
With T1s, though, you cannot aggregate, at L2, more than a single T1's bandwidth, without doing something like MLPPP, or using some kind of MUX.
At L3, you can do packet by packet, round-robin, on multi links, but packet delivery sequence (for a single flow) is not guaranteed. MLPPP does guarantee this.
"What about MLPP split flow's packets?"
Yes (unlike Etherchannel which does not.)
"Will this work with 4 times bandwidth(binding 4 T1)?"
Yes.
"If one T1 is down, will it reduce to 75% bandwidth?"
Yes.
"How about QoS? Can it run on this MLPPP?"
I believe you can configure and use QoS on a multilink interface.
