Interestingly enough, cucumbers do get a shout out in the Torah, when the Israelites are complaining about having only mana to eat in the desert:
זָכַרְנוּ, אֶת-הַדָּגָה, אֲשֶׁר-נֹאכַל בְּמִצְרַיִם, חִנָּם; אֵת הַקִּשֻּׁאִים... "We remember the fish, which we were wont to eat in Egypt for nought; the cucumbers..." (Num. 11:5)
I think nowadays קישוא refers to a zucchini--though Wikipedia says that a synonym for מלפפון is קישוא הגינה ("zucchini of the garden")
https://www.haaretz.co.il/magazine/the-edge/.premium-1.2015430 is a short and deep study into קישוא and מלפפון in Hebrew. Seems that at the Chazal time קישוא was probably cucumber, and מלפפון was zucchini (or some squash, or in any case some variety that's usually cooked). But then at the late 19th century the first Hebrew-as-daily-language speakers picked these two words but crossed their reference. The learned linguistics tried for several decades to fix this, but in vain.
no. there are many biblical names that we use this days but not the same (for example oat (I mean common oat) is a biblical name, but what we call this days oat isn't the same kind of cereal. the same goes for pepper (from hazal, not from the Torah), and the modern mandragora isn't the same flower as the biblical flower. that happens also with colors and the names of the stones that make up the priestly breastplate