Share classes and running costs

trickydicky14

Can you help, currently I have money invested in VLS 60 with Charles Stanley within an ISA which I am comfortable about, I have now got a few thousand from an ISA just matured and was thinking of possibly investing this in to L&G multi index 3 or 4?
I have several questions:

1. The L&G funds come in what I assume are two share classes C & I, what is the difference?
   
2. the C class is cheaper to run but C.S don't allow this to be put into an ISA/NISA but the I class which is more costly can go into this wrapper, I know I risk looking dumb but why is this and why the difference in costs TER/AMC.

1. Do you think the L&G multi funds are sufficiently diversified / complimentary to make this worth doing along side my VLS 60 and would the L&G 3 or 4 be around the same risk level.

Yes I know I have much to learn so if you can help me on my way I would be most appreciative.