Can anyone out there point out the coding guidelines we need to follow for Roku development?
Also want to know
function name should start with uppercase or lower case
There are no coding guidelines. Pretty much code however you like. There's some criteria for published channels, but they have nothing to do with coding style.
The language reference has the rules for things like Typed variables. Almost nothing you do is case sensitive. But coding rules and formatting, whatever you want (so of course that means Tabs!)