My iPhone is lost/stolen and I didn't have a password on it, lost mode is on pending due to the phone being off and cell data is off as well being that I'm in another country. Will lost mode goes into effect once the phone goes on? Are they able to see all my pics and data being that it was not password protected?
If the phone ever gets an internet connection again it will go into effect, yes.
However if your phone was stolen, you risk that the thief will wipe it and sell it off - probably as parts - and your lost mode setting will be for nothing.
As you have no pass code on the phone, they will be able to see all your pictures and data, yes.