1)Yes, you can have an if statement with strings, like
if myteststring = 'abc' then
2)To skip an iteration, you would have to keep track of the iteration number and check for it each time
if myiteration <> 10
do some stuff
else
don't do anything
3) I have never had luck reading an empty excel cell. We ended up putting a character in the field that didn't mean anything and using that as if it was empty.
if myexcelcolumn <> ')" then
do some stuff
else
don't do anything
