If it's about Google software which uses a phonetic way of typing in Tamil which you are reviewing about, then why did anyone have to add the Hindi screenshot at the beginning? It seems inappropriate. There is no reason to include Hindi. I know the Google keyboard layout tool supports other Indian languages, as well. But let's just keep it simple and stick to Tamil alone, i.e particularly when you are reviewing about a tool which write in the Tamil language.
a = ?
A = ?
aa = ?
?? = ஷ
?? = ஶ
?? = ச
?? = ஸ