@Iyapo1
Those quests will be able to be declined after you are 'in' the next chapter. Being 'in' the next chapter is defined by the game as having unlocked the first tech for the next chapter (Advanced Scouts for most chapters). The remaining quests for the previous chapter will then come up, in order, with the option to accept or decline. This only causes issues if you want the rewards for a quest, but the quest is worded in a certain way that makes it hard to complete. Example of wording that would cause a problem for culture bldg quests: If the quest says 'Have xxx culture bldg' and you've already built it, you'll be able to accept and get the rewards. If the quest says 'Build xxx culture bldg', having the building already built won't satisfy the quest; you'll either have to sell it and rebuild it or build another one.
Where this becomes an overall issue is in the guest race chapters (Ch6-dwarves and up). Some of the quests to 'sell the portal' for the previous guest race award 200 diamonds (I haven't met a player that doesn't want that reward, lol!). If you've already sold the portal, you'll have to rebuild it and then sell it off. A change was made at some point so you can build and sell off any of the portals to satisfy those quest requirements in higher chapters. Example: Much easier/cheaper/faster to build a lvl 1 Dwarven portal (2x2, costs 355K coins and 12.4Ksupplies, and takes ~16.75hrs) than a lvl 1 Sorcerer's & Dragons portal (Campus) (7x7, requires 1470K coins, 103K supplies plus crystal, scrolls and silk and takes ~23.5hrs).