Is there any usefullness in doing these things on a speed bag?

Majority of the time when people ask this question it's cos they don't know to hit a speed ball,

I like doing 3 rds at the end of a session to cool down,

 

Nothing. Waste of time. I suppose it makes you look cool...

 

Nothing, boxing-wise. Years ago, pre-Internet, there was a Goosen-produced videotape featuring the Ruelas brothers that featured some good, practical, boxing oriented speed bag drills.
Some trainers like to use the speed bag at the end of a workout, in the belief that when you are tired, there is some benefit to that last couple rounds of keeping your hands high.

 

with regard to boxing you are correct

training in general not so, I can do all this ****, its nice for a cool down and you can up your pace depending on the bag plus it can keep you thinking and its fun to learn something new every now and then

kinda like the rope tricks and stuff I guess

 

I honestly think that the speed bag in general is not specific for boxing , I mean you stand to it straight on

 

I think that as well, in the context in which it generally used. I've read some old, like 1920s or before old, training books where they talked about something completely different, and that sounds more relevant, but I've never pursued it.

 

no benefits at all. this is all show no go, theres countless guys on youtube who are just speedbag hobbyists with no real interest boxing skills at all

 

There is a purpose to this, it will drive your neighbors insane.