yep.
your hub probably won't be scrutinized, but you have to make sure the cog won't undo when you apply back-pressure to stop (you'll do quite a lot of this on induction)
if you can assure that it will stay on tight, then you can use it. Otherwise you should consider the safety of yourself and other riders as if one person in the bunch has a failure, it can bring a lot of people down.
The free hire bikes are perfectly decent, in any case.
yep.
your hub probably won't be scrutinized, but you have to make sure the cog won't undo when you apply back-pressure to stop (you'll do quite a lot of this on induction)
if you can assure that it will stay on tight, then you can use it. Otherwise you should consider the safety of yourself and other riders as if one person in the bunch has a failure, it can bring a lot of people down.
The free hire bikes are perfectly decent, in any case.