The condom must be put on before there is any pre-ejaculatory fluid. It is not enough to put on the condom just in time to prevent contact with semen. Kissing is probably safe if neither person has cuts or sores. There may be some slight risk from saliva. Oral sex is probably safe as long as ejaculation does not take place in the mouth.
Safety is relative.
The above sex practices are safe in the sense that they involve relatively low risk of exposure to life-threatening disease. Oral sex which involves ejaculation without a condom is not safe. Any practice which involves contact with cuts, sores or raw areas is not safe. Remember, even small or microscopic cuts can be dangerous. Any practice which involves contact between any body fluids of the partners is not safe.