since u have done house job in pakistan and comply with min 3 months of medicine and surgery, u should be ok to apply for a licence to practice once u have cleared both parts of Plab exams. I would recomend to visit GMC website which gives detailed explanation and information on what to do and expect.
Training jobs are like specializations, other jobs are like trust SHO.. these are normal doctors in various departments in hospitals here. So once u have the licence to practice, u can apply for these jobs.
Training jobs are hard to find and depend on number of things like what specialisation u are applying, where u live, and how u have developed your portfolio once u have started working here.. u need to apply for training in November for the positions starting the following years in August. NHS normally prefers to allocate the training positions to British +Europeans, then people who dont have restriction and then if all the seats are not filled, these are allocated to Non -EU personnel like yourself. Once this happens, they can get you a visa, which is not a big deal for most of the trusts.
Hope this makes sense