1-- General Factory Work, I suppose, would be for any job there that did not specifically involve making/assembling-- the maintenance staff, shippers and boxers, assistants, etc. If someone is hired for 'general factory work' the job responsibilities often vary during the day or week, the worker being assigned various tasks, and are generally at a lower skill level than production workers per se. Having said this, many companies could easily lump or overlap the two categories, I think.
2-- Electronic production work would involve making and assembling electronic products-- which include virtually all the household appliances and labor-saving devices we use today. Extruding or other manufacturing steps in the manufacture of components and their assembly into computers, calculators and microwave ovens would be tasks on the production line.
3-- No; they are payed according to time worked. Workers paid on the basis of output are doing
piecework.
4-- Assembly jobs in my mind are just that-- all the steps required to put a finished unit together after the individual components are manufactured. This may be done on an assembly line (many workers in turn taking part) or at individual work stations, where each worker assembles his own units.