While lucid dreaming is it possible to extend REM cycle?
We can force ourself to wake while dreaming or force ourself to move during sleep paralysis. In a sence, overriding a brain function.
there are ways to prolong (lucid dreams), by rubbing ur hands really hard, moving ur eyes really fast, spinning and such, will often lead to lengtening the REM-Cycle. Or Cause False Awakenings, => lol, thats still lengthening the REM-Cycle ^^"
Hi dusordusld 
welcome to LD4all 
Yes, there are many methods to extend REM dreams. Fadem mentioned some good techniques. Especially the spinning technique and rubbing your hands seem to work pretty well. But still there are often differences between people, so it’s best to check out several methods and see which one works best for you.
Good luck! 
These techniques are to extend single dreams in one REM cycle. The cycle itself cannot be altered, at least not as far as I know. However, you can stay lucid throughout all sleep/dream phases if you get really good at it, so it’s not really useful anwyay to extend REM cycles.
I would say yes and no. To some extent you can play with your rem cycle, induce rem at sleep onset, possibly extend rem a little bit. However, I do agree with Xetrov you may be able to bend the rules a bit but you can’t break them. ( As far as I know)Also keep in mind that you can dream in other stages of sleep. Sometimes I think we put too much emphases on REM sleep.
Yes, I don’t think expanding REM cycles is possible without some medication that would alter the neurotransmitter or hormone balance. Anyway, in the morning hours, you REM cycles will last up to 1½ hrs, and if you can maintain a LD that long, I think that’ll be enough for most things.