Hi I have a 1.1.2 OTB Iphone with BL 4.6 which I software unlocked via the first of the software unlocks that became available and I Jailbroke it, I forget the name of the method. My question is can I upgrade to 1.13. and if I can do I have to Jailbreak it again or is it just a matter of upgrading via Itunes? please help

yes you can upgrade.
you have to jailbreak+activate+unlock again.

BTW, why do you want to upgrade?
If your phone is 1.1.2 working now, I said you should spend more time reading this forum. Find out if the upgrade is right for you and it is what you wanted. Once upgraded, some apps may not work and you have to do more work to get things working again. So, read and be aware of things you have to do (if needed).

Questions like: how do I save my contact, how do I save my data, this & that does not work .... and etc ....
I've seen so many people jumped at the upgrade and ended asking endless questions (most have been answered already).
Do you homework first because ultimately it's you who have to understand and do the work.

Lots of nice people are here and willing to help but sometimes they are not around when you need them