Ah Richard got to reply before me, agree with his reply realy
Picture 1, the threaded hole is for fixing the front part of a fully enclosed chain guard, if there is a threaded pipe in there my guess is a PO has had a pipe from the crankcase breather exit to the threaded pipe as a meams of lubricating the chain ( popular modification )
Picture 2. Some levers do have an internal thread (most I think) but it may well work ok as it is if you screw the nut on the cable adjuster up to the lever
Picture 3. not sure - the brake arm looks to be a bit past the optimum working angle but that is assuming it was at rest when you took the photo, might be your brake shoes are worn.
Picture 4. yes you should have an adjuster or a ferule, depends upon the boss that the cable comes through there are two types, one has a threaded hole if I remember right and also different size of hole, if you could measure the hole it would help as someone might have a slotted ferule rolling about their shed.
All the best - Bill