I'll counter the " don't turn the engine backwards " ,even though the manual says not to turn backwards, if the chain skips, it was badly worn to start with. The manual recommendation was likely so a worn chain would not come off while the car was in the shop leaving the shop to explain to customer that the previously running engine needs to come apart for a major repair.

Engines tend to stop against compression and can roll back a bit to varying degrees. The camshaft can also roll over a lobe causing it to snap forwards giving a similar effect to rotating the crankshaft backwards.

In the day, gasoline engines would get " run on " where the engine would continue to run ( poorly ) when the ignition was shut off, sometimes the engine would violently run backwards for a bit.