Can anyone help me out why there is a change between two multi option selection interface for two different bots.....and how to change to the basic one!!

Do you have the same number of possibilities in both chatbots?

Yess

Are the number of items in the list the same? I think, and this is from my experience, if you have fewer items in the list, it shows differently. Again I may be wrong, but you may test it out

I'm pretty sure it is related to the number of choices or lenght of choices The drop-down is used instead of little bubbles to avoid taking up lots of space on the chat