Do i have to sleep the same Everynight in order to increase Chances?

Sometimes we're either too busy with stuff or want to watch movies.
OR we're too excited doing some kind of hobby, so we go to sleep at night.

I might end up sleeping at times just 5 hours.
in fact that's what's been happening lately.

I hear that REM doesn't happen till 4.5 hours, so that means i almost have no chance of reaching REM.

So should i just sacrifice hobbies and activities( Which is fine) and just go to sleep at 8pm or something like that? and get my 8 hours of sleep.

REM starts at like 90 minutes.

You don't have to sleep at the same time every night but it certainly helps. Generally, sleep cycles are about 90 minutes long, with REM coming at the end and becoming longer with each cycle.

You could switch to a bi-phasic sleep schedule, sleeping 5 hours of core sleep with a 90 minute nap in the middle of the day, or 6 hours with a 20 minute nap in the middle of the day. The nap would be mostly REM.

You do not have to sleep the same time every night , but it helps tremendously ^^