You cannot open modern 1.20 worlds in 1.8.8. The terrain generation changed drastically in 1.13 (The Update Aquatique). If you load a new world in 1.8.8, it will generate a "Pre-1.13" world with no oceans deeper than 20 blocks.
If you have ever watched a Minecraft PvP montage, you saw the "1.8.8 click." Without the cooldown bar introduced in later versions, players utilized "Jitter clicking" or "Butterfly clicking" to register 10-15 hits per second. The knockback algorithm in 1.8.8 is also distinct—it allows for "W-tapping" (resetting your sprint mid-air) and "block-hitting" (alternating between left and right click to reduce incoming damage while dishing it out). Minecraft 1.8.8