we could define "złożyć wniosek o wotum nieufności" as "successfully submit a motion of no-confidence". whereas składać would mean attempt to submit.
The imperfective aspect in "PO (czterokrotnie) składała wnioski (wniosek) o wotum nieufności" means that repetitive action was in progress and the emphasis is really on the action rather than on the result. The result is irrelevant here, tbh.
Whether the motions were rejected or not, the imperfective aspect would be most likely used in both cases as the emphasis is on the process itself which is usually fussy, noisy and lasts for a period of time. The result is pretty obvious from the very beginning - the motion submitted by the opposition is typically rejected and the opposition knows it. The whole thing about it is not the result, but the action and the fuss surrounding the acts hence it is natural to use the imperfective aspect for a repeated submission of a motion.
We will of course say: "PO złożyła wniosek o wotum nieufności" after a motion was submitted.
5 W zeszłym roku przeczytałem książki cały czas
This is incorrect since the phrase "cały czas" implies the continuity of an action. The perfective aspect of the verb adjoined to such a phrase makes it look really weird.