Hi Abhishek,
First of all this is not the nested transaction. Please check this to understand more on
Netsted Transactions. This is just one of the links I found on google.
When you call another transactional method ( Requires_new) in another SLSB, it suspends the existing transaction and then starts a new one.
Additionally your timeout in one method will not be able to stop the processing of another bean's method. There is no notification mechanism between them , isnt it?
For that you will need to poll some kind of variable which will tell you if timeout has happened and stop the FOR loop.
Regards,
Amit