1) The functional gr should get lowest no.
2) It depends on what is the other subtituent to which it is attached.
3) both can both cannot,becoz both are same dosent matters which one is getting lowest no.
4) this is becoz ethyl ethanoate is trivial name or common name where as methyl propanoate is International Union of Pure and Applied Chemistry (IUPAC) name
5) yes it can be wherever necessary
6) Of course the first carbon containing double bond present in the chain will get the lowest no.
I'm in class 12 so you can rely on my answer m giving u 100% assurance.