1. I've pressed close/isolate on the outer door buttons, front and back of the train, but the middle doors still opens can you isolate this door too? 2. Are there any pacer 142s like this one with two doors instead of folding doors ?
You can't effectively isolate the middle door in TSW because there's no way to lock it out. The middle doors don't have any panels on the outside or inside. On the real Pacer units, there's a slot for the T-key/carriage key which inserts into the panelling vertically above the door (so above your head as you walk in the door under the same panel where the guard operates the doors from). This slot locks out the door so that it can't be opened in case of short platforms or malfunction. As for the second question, there aren't any Pacers with the 2 leaf doors simulated in TSW. This is due to the fact that the units in TSW are based on their 1980s configuration. The 2 door version was a later modification to the units.
More precisely, the Class 143 and 144 were built with Alexander (bus) bodies instead of the Class 141 and 142's Leyland (bus) bodies. The four-leaf doors came with the Leyland body, and the two-leaf doors came with the Alexander body. Much later, after Leyland parts became scarce, Alexander doors were retrofitted to the 142s to improve reliability. I think this would have happened in the 21st century, so well after the era modelled. By then, the 141s (with narrower bodies and less reliable mechanicals) had all been shipped off to Iran. The original mid-1980s configuration Pacer is the one used for the Blackpool route's Journey Mode and AI services in Timetable Mode. However, two later configurations are also provided. The differences are that the SCG four-speed gearbox was fairly quickly changed for a Voith T211r (similar to that used on most Sprinters) because the SCG one was hilariously unreliable; this had materially delayed the withdrawal of even the more worn-out examples of 1st-generation DMUs. Later the Leyland engine was changed for a Cummins one, allegedly because it would cost less to buy a complete new Cummins engine than to overhaul a Leyland! The Cummins provides about 15% extra power, as a bonus, and is thus a little bit better matched to the Voith transmission's capacity. This evolution was completed in the mid 1990s, and the 143s and 144s went through roughly the same process since they were originally built with the same drivetrain.
