Hi Vinay!
1. You could use UDF which I posted in your previous thread. It has a parameter for substring length and splits input string of variuos length into substrings of diven length.
2. If you have one value in input queue for context, you can map it to target tag as: SourceField -> MapWithDefault[0] -> TargetField.
3. Use standard function Index with parameter "Reset by context change".
Regards, Evgeniy.