Simple Set of Rules for mean Reversion

The problem with that specification is, we are not telling the scan engine how many bars ago price closed below the 5 ema, and we are not telling it how many bars to look back for 3 lower lows. Also, we are not specifying which bars are the lower lows. The scan engine does not have variables, so we can't just inspect each bar and ask whether it's a lower low because we can't keep a running total of hits on a lower low.

If you want the cross below to be four bars ago, and each bar since then has been a lower low, that can be done because it is specifies an exact pattern. The problem with specifying an exact pattern is (as you've probably noted), they rarely re-occur.

If you have found that there are a limited number of variations of cross below and three lower lows, you would write out each alternative and connect them with "or". This is a significant time investment, so you would have to work that out yourself.

Alternatively, you could write a scan for condition 1,2 and 4, put the results in a list and then watch the list for the remaining condition.