Yes you can log IF on a dark horizon less night clear of cloud.
Unless the rules changed recently you have to be in in cloud to log IF in Australia other countries have different rules and interpretations.
If you fake IF time you'll get caught at a interview as most people will expect IF time to be within a specific ratio of total time. You will have a hard time explaining 1500 total and 1000 IF unless you were doing night freight in Tasmania or New Zealand.
It's people who fake twin time and shaft everybody to the decent jobs are the guys who should be hung drawn and quartered and I believe a few have over the years.